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A 57658 7

ARTES
1837
SCIENTIA
LIBRARY
VERITAS
OF THE
UNIVERSITY OF MICHIGAN
PLUNIDUS
TCEBOR
SI QUER'S PENINSULAM·AMⱭINAM
CIRCUMSPICE
SCIENCE
LIBRARY
QE
367
.C466
;
CHAPMAN'S
MINERAL CHARACTERS.
In 8vo. cloth, with numerous Illustrations, price 7s.
PRACTICAL MINERALOGY;
OR, A
COMPENDIUM OF THE DISTINGUISHING CHARACTERS
OF MINERALS.
By which the Name of any Species or Variety in the Mineral
Kingdom may be speedily ascertained.
With 305 Illustrations, and a copious Index.
BY EDWARD J. CHAPMAN.
OPINIONS OF THE PRESS.
"This work was a great desideratum, and we rejoice to see it so ably exe-
cuted. The student and mineralogist could have no better guide."-Literary
Gazette.
"Mr Chapman's very creditable work, however, is free from the principal
objections of former ones. It is compendious, yet not too brief; it is, in fact,
just such a work as was wanted, and will lighten the labours of many a pro-
ficient mineralogist. A production more effective of its object, whether that
of an old or young author, we have not met with."-The Chemist.
"This volume will be found of the greatest importance, both as a work for
study and of reference. The method of classification adopted brings the whole
complicated system into the most simple form before the student."-Mining
Journal.
"This work is a very creditable production."-Geologist.
"The work before us is certainly far in advance of its predecessors in this
respect. Its arrangement is remarkably simple, and its expositions perspic-
uous and comprehensive. In addition to upwards of 300 lithographed figures,
there is added a long and copious index, forming a complete table of syno-
nymes for all English, German, and French authors."-Atlas.
London: H. BAILLIÈRE, Publisher, 219 Regent street.
A
BRIEF DESCRIPTION
OF THE
CHARACTERS OF MINERALS:
FORMING A
FAMILIAR INTRODUCTION
TO THE
SCIENCE OF MINERALOGY.
BY EDWARD J. CHAPMAN,
AUTHOR OF PRACTICAL MINERALOGY.'
WITH THREE PLATES.
LONDON: H. BAILLIÈRE, PUBLISHER, 219 REGENT STREET.
PARIS: J. B. BAILLIÈRE. LEIPSIG: T. O. WEIGEL.
1844.
LONDON:
PRINTED BY REYNELL AND WEIGHT,
LITTLE PULTENEY STREET.
Mineralogy
Sark
11-10-25
12219
ADVERTISEMENT.
THE following pages are intended as an intro-
duction to my Treatise on Mineralogy,' lately
published by Mr Baillière, of Regent street, or as
an easy introduction to the science in general.
They have not been written for the perusal of
the advanced mineralogist, as their contents must
be of course already familiar to him, but are
offered to the unassisted student, as a simple and
easy means of gaining a sufficient knowledge of
the details of the science, as to enable him (with
the assistance of the above-named work) to dis-
vi
ADVERTISEMENT.
tinguish any mineral substance that he may chance
to meet with.
An elementary description of the principles of
any science must necessarily be in part derived
from the combined labours of preceding writers ;
the present brief essay will be found, however,
to contain no inconsiderable portion of original
matter and observation, and I am not aware of
any other volume comprising so complete a unión
and exposition of the two principal divisions of
mineral characters.
I have annexed a list of the works which have
assisted me (in some instances very materially) in
the construction of the following pages.
WERNER'S External Characters of Fossils.
MOHS's Mineralogy, vol. i.
ROSE's Crystallography.
BEUDANT'S Traité de Minéralogie, vol. i.
BERZELIUS'S Blowpipe Treatise.
GRIFFINS'S Chemical Recreations.
ADVERTISEMENT.
vii
i
FRESENIUS'S Qualitative Analysis.*
CHAPMAN'S Practical Mineralogy.
Northampton, Feb. 3, 1844.
E. C.
* A translation of this excellent work has lately been given
to the British public by Mr BULLOCK. The work, however,
treats only of those elements and their combinations which are
employed in pharmacy or the arts; all mention of titanic acid,
tungstic acid, zirconia, selenium, &c., being designedly omitted,
and this omission renders it incomplete for the purposes of the
mineralogist. A defect like this (for it is surely such) might
have been easily remedied without having greatly increased
the cost and bulk of the volume.
CONTENTS.
PRELIMINARY OBSERVATIONS
THE EXTERNAL CHARACTERS
Aspect, or Kind of Lustre
Colour
Hardness
Specific Gravity
Streak
Form
1. Regular Form
A. Preliminary Remarks
B. Principal Forms of Crystals
C. Theory of Primary or Primitive Forms
D. Systems of Weiss
E. Method of describing Crystals
F. Modification of Rose's Catalogue of Crystallized
Minerals
2. Irregular Form
Structure and Cleavage
Surface
Tenacity
Transparency
Degree of Lustre
Fracture
Form of Fragments
Frangibility
PAGE
1
2
3
4
7
10
13
14
15
id.
17
•
24
26
28
32
*45
45
47
48
49
•
50
51
52
id.
X
CONTENTS.
Flexibility
Touch
Soiling
Odour
PAGE
53
id.
id.
54
•
id.
Sound
Adhesion to the Tongue
Taste
Magnetism
Electricity
Phosphorescence
THE CHEMICAL CHARACTERS OF MINERALS
Action of Acids
Description, Manipulation, and Action of the Blow-
pipe, and of its Accompanying Apparatus
Preliminary Remarks
A. Description of the Blowpipe
B. Of the Combustible for the Blowpipe Flame
C. Method of using the Blowpipe
D. Different Parts of Flame
E. Size and Shape of the Assay
F. Supports for the Assay
F. 1. Charcoal
F. 2. Platinum Forceps
F. 3. Platinum Foil
F. 4. Platinum Wire
•
F. 5. Glass Tubes (closed)
F. 6. Glass Tubes (open)
55
id.
•
id.
· 56
60
61
id.
62
id.
63
•
66
68
•
70
•
71
72
id.
73
75
76
·
•
77
•
78
79
•
83
•
•
84
86
•
id.
•
G. Other necessary or useful Instruments
H. Blowpipe Reagents, and Method of using them
H. 1. Carbonate of Soda
H. 2. Borate of Soda
H. 3. Microcosmic Salt
CONTENTS.
xi
H. 4. Bisulphate of Potash
H. 5. Nitrate of Cobalt
H. 6. Nitre
H. 7. Tin
H. 8. Silica
H. 9. Oxide of Copper
H. 10. Bone Ashes, and Refined Lead
H. 11. Test Papers
H. 12. Other Reagents
I. Simple Blowpipe Operations .
I. 1. Oxidation
I. 2. Reduction
I. 3. Roasting and Sublimation
•
FAGE
87
id.
88
id.
•
89
id.
90
id.
•
L
id.
91
id.
I. 4. Trial of Fusion, &c.-Characters developed
during the Trial.-Results of the Trial
I. 5. Production of Coloured Flames
I. 6. Flaming
ུ དྲྭ་ ཾ་
93
96
99
. 100
101
•
•
102
I. 7. Cupellation
K. General Method of examining a Mineral Sub-
stance
APPENDIX:-A Brief Compendium of the Elements of
Qualitative Mineral Analysis.
I. Preliminary Remarks
II. Discrimination of the Class or Order to which a Mineral
may belong, and Detection of its Component Elements
105
109
•
ADDITIONS.
The following figures have been added to PLATE II, since the
article Form (p. 14) was in type.
Fig. 12 a. The cube with truncated angles, forming the
transition into the regular octahedron, fig. 3. See p. 18, line 1.
Fig. 10 a. The regular hexahedral prism and pyramid, de-
scribed at p. 28 as the common form of quartz crystals.
Fig. 12 a.
line 13, et seq.
The four-sided right square pyramid. See p, 22,
ERRATA.
Page 20, line 14, for Fig. 10 read Fig. 12.
line 20, for Fig. 18 read Fig. 13.
Page 22, line 6, for Fig. 11 read Fig. 10.
A
BRIEF DESCRIPTION
OF THE
CHARACTERS OF MINERALS.
PRELIMINARY OBSERVATIONS.
EVERY mineral substance possesses two distinct sorts
of characters, by one, or by a combination of both, of
which, it may be distinguished from other substances.
These two sorts of characters are generally termed
the "external" and "chemical" characters :-the
former being those which are immediately apparent to
our senses, or which may be rendered so, without
destroying the natural state of the mineral; and the
latter being those which are only made evident by, or
during, the chemical decomposition of the mineral, by
means of various reagents with or without heat, or by
means of heat alone.
B
2
CHARACTERS OF MINERALS.
+
THE EXTERNAL CHARACTERS.*
These characters (as given below) are rather nume-
rous, but the student will find that the whole of them
are not possessed by any one mineral; several of them
being, in fact, only applicable to a very few sub-
stances, and of course, as such, highly characteristic,
though of limited utility. Others, though generally
applicable, are of little utility, from their indistinct-
ness; but those at the commencement of the following
list, are not only generally applicable, but also in most
instances highly characteristic, particularly when com-
bined.
Aspect, or Kind of Lustre.
Colour.
Hardness.
Specific Gravity.
Streak.
Form.
Structure and Cleavage.
Surface.
Tenacity.
Transparency.
Degree of Lustre.
Fracture.
Form of Fragments.
Frangibility.
Flexibility.
Touch.
Soiling.
Odour.
* Including the characters sometimes termed "Physical."
THE EXTERNAL CHARACTERS.
3
૭
Sound.
Adhesion to the tongue.
Taste.
Magnetism.
Electricity.
Phosphorescence.
Aspect; or Kind of Lustre.
(L.)
A character of considerable importance. The fol-
lowing tabular view exhibits its chief and subordinate
divisions; the terms, by means of the examples given,
will explain themselves.
Metallic
Aspect.
Non-metallic
Aspect.
Metallic-Ex. Native Copper; Iron Pyrites.
Semi-metallic, or imperfectly Metallic-Ex.
Chromate of Iron.
Adamantine:-Ex. The Diamond.
Vitreous:-Ex. Rock Crystal.
Resinous:*-Tungstate of Lead.
Pearly:-Ex. Margarite; Satin Spar (a var.
Silky:
of Calcite).
Indefinite:-Ex. Lithomarge.
Note. These kinds of lustre are often blended in the same
mineral. Thus we have metallic-adamantine: Ex. Anglesite;
metallic-pearly: Ex. Bronzite; vitreo-resinous: Ex. Vesuvian;
vitreo-pearly: Ex. Cryolite; &c. Many minerals possess also
two distinct kinds of lustre, one externally, and the other in-
ternally. Thus Stilbite has a vitreous external, and a pearly
internal, lustre; in which case both should be noticed, though
it must be generally borne in mind, that the characters of mi-
*Greasy or waxy in appearance.
4
CHARACTERS OF MINERALS.
nerals as developed on their newly-fractured surfaces, are always
more to be relied upon, than those taken from the external sur-
faces, and this particularly applies to the two following cha-
racters-Colour and Hardness.
The true metallic lustre may be always distinguished from
the metallic-pearly or metallic-adamantine lustre, by the two
following signs, namely: by being always combined with perfect
opacity, and by remaining unaltered on the scratched surface,
the others being often combined with transparency, and losing
always their false metallic lustre upon being scratched with the
knife; thus Bronzite in the streak becomes of a dull greyish-
white.
Colour.
(C.)
A character also of considerable importance when
combined with a metallic aspect, but when joined to
non-metallic lustre, of little use except in some few
peculiar cases. For instance, we have varieties of
Fluor Spar, Quartz, &c., of almost all colours, whilst
the Crocoisite (chromate of lead), Orpiment, Real-
gar, and a few other minerals, possess but one. The
different colours also have different degrees of impor-
tance; thus, white being common to a vast number of
minerals, is far below red as a "characteristic," the
latter being confined to a few.
The non-metallic colours are:-white, grey, black,
blue, green, yellow, red, and brown, with their various
shades and intermixtures: as reddish-brown, greenish-
black, &c.; and sometimes the peculiar shade of
THE EXTERNAL CHARACTERS.
5
colour is expressed by reference to well-known or
familiar objects; as orange-yellow, blood-red, violet-
blue. The depth of colour is also often mentioned;
as light or clear greyish-green, pale blue, dark cherry-
red.
The metallic colours are:-
White
Grey
Black
Yellow
Red
{
Silver-white: Ex. Native Silver; Mispickel.
Tin-white: Ex. Native Antimony; Native Mer-
cury.
The tin-white colour possesses a slight shade of
bluish-grey.
Lead-grey, the colour of pure lead, a metallic
bluish grey: Ex. Galena; Stibine; Molybde-
nite.
Steel-grey, the colour of steel, a metallic blackish-
grey: Ex. some varieties of Grey Copper; Syl-
vanite; Manganite.
Iron-black: Ex. Aimantine; Pyrolusite; Miar-
gyrite.
Brass-yellow, a clear metallic yellow: Ex. Cop-
per Pyrites; Radiated Iron Pyrites.
Bronze-yellow, a metallic brownish-yellow: Ex.
Magnetic Iron Pyrites.
Gold-yellow, a pure deep yellow: Ex. Native
Gold.
{ Copper-red: Ex. Native Copper; Nickeline;
Phillipsine.
In addition to the above, we have also to notice
several other properties appertaining to this character,
if they be present in the minerals under examination.
These properties are the following:-
B 2
6
CHARACTERS OF MINERALS.
The disposition of the colours,-which may be either uniform,
or in stripes, spots, veins, &c.
The play of colour, -as exhibited by the precious variety of
Opal, the Labradorite, &c.; and which consists in the mutable
reflection of various bright colours, upon turning the minerals
which possess it, to and fro in the light.
Iridescence,—a reflection of the prismatic rays, chiefly arising
from fissures in the interior, or from the lamellar structure of
the mineral; the former being observed in iridescent rock
crystals, the latter, on the terminal plane of the pyramidal
crystals of Apophyllite.
Opalescence,—a reflection of a floating milky-light from the
interior of the minerals which possess it, as the Cat's-eye, the
adularia variety of Feldspar, some varieties of Corundum, &c.
The variety of the last-named mineral, called "asteria sap-
phire," owes its beauty and value to the possession of a mutable
opalescent star of six rays, evidently arising from structure.
This character (opalescence) is often termed "chatoyance," and
it should perhaps (as remarked by WERNER) be rather con-
sidered as a mutable reflection of lustre than of colour. The
silky lustre is, in fact, a variety of opalescence.
Tarnished colours.-These occur chiefly on the surfaces of
minerals possessing a metallic lustre; but, in some instances,
the tarnish extends through the entire mass, as in the Phillip-
sine. The tarnish may be either simple, consisting of one colour;
or variegated, consisting of several colours. The terms "rain-
bow tarnish," "pigeon's neck tarnish," &c., sufficiently explain
themselves.
Dicröism. This is the property of exhibiting different colours
where viewed by transmitted light in opposite directions. The
Iolite, and some varieties of Tourmaline and Mica, are examples
of this curious character.
THE EXTERNAL CHARACTERS.
7
Hardness.
(H.)
This is one of the most important and useful of
mineral characters, and it may be very definitely
noted by means of the comparative scale of Professor
Möhs, now universally adopted. This scale consists
of the following ten minerals, of progressive degrees
of hardness, to some one of which, by a simple com-
parative process, the hardness of all other minerals
can be referred, or approximated.
1. TALC, of a greenish colour.
2. ROCK-SALT, a pure variety.
3. CALCAREOUS SPAR, a cleavable variety.
4. FLUOR SPAR, a cleavable variety.
5. APATITE, the variety from Salzburg.
6. ADULARIA FELDSPAR.
7. ROCK CRYSTAL, a transparent variety.
8. TOPAZ.
9. CORUNDUM.
*
10. THE DIAMOND.
The following is an account of Möhs's description
of the method of using this scale. When we wish,
by means of this scale, to ascertain the hardness of a
* As the diamond is the only substance which corresponds
to this degree, the scale may of course terminate at No. 9, and
the minerals composing it will then be within the means of all.
8
CHARACTERS OF MINERALS.
mineral, we first try which of the members of the
scale is scratched by it. In order to save the spe-
cimens of the scale, it is advisable to begin with the
highest members, and proceed downwards, until we
reach the one which is scratched. We next take a
fine hard file, and draw along its surface, with the
least possible force, the specimen we are examining,
and also the two members of the scale with which
it appears to agree the nearest in hardness. From
the resistance these bodies oppose to the file, from the
noise occasioned by their passing over it, and from
the quantity of powder left on its surface, we estimate
securely their relative degrees of hardness. When,
after several experiments, we are satisfied as to which
member of the scale the mineral under examination
is most nearly allied, we attach to it the numeral be-
longing to that member, as given above, and say—
supposing its hardness to be equal to that of fluor spar
-H. 40, or to that of apatite H. = 5·0, or
if it do not exactly agree with either
thus placing it between the two.
K
H. = 4.5,
As a useful appendix to the above, the following
note (reprinted from my late treatise*) may not be un-
acceptable to the student.
“As the minerals comprising the scale of hardness
constructed by Professor Möhs may not be always
* · Practical Mineralogy,' &c.
THE EXTERNAL CHARACTERS.
9
at hand, especially in travelling, the following scale,
exacting only objects always to be met with, and
which agrees in its most essential respects with that of
Möhs, may be sometimes found convenient, but the
minerals and file should always be used in preference,
if possible."
CHAPMAN'S CONVENIENT SCALE OF HARDNESS, TO
CORRESPOND WITH THAT OF MÖнS.
1. Yields easily to the nail.
2. Yields with difficulty to the nail, or receives merely an
impression from it. Does not scratch a copper coin.
3. Scratches a copper coin, but is also scratched by it, being
of about the same degree of hardness.
4. Not scratched by a copper coin. Does not scratch glass.
5. Scratches glass, though rather difficultly, leaving its powder
on it. Yields easily to the knife.
6. Scratches glass easily. Yields with difficulty to the knife.
7. Does not yield to the knife. Yields to the edge of a file,
though with difficulty.
8, 9, 10. Harder than flint.
Note.—2.5 scratches a copper coin slightly, and 3′5 is scratched
by one in about the same degree.
10
CHARACTERS OF MINERALS.
Specific Gravity.
(Sp. gr.)
The high importance of this character was fully per-
ceived by the older mineralogists, almost at the dawn
of the science.
The specific gravity of a body, is its weight com-
pared with that of another body of the same size or
volume. This latter body is assumed as a standard,
and the standard with which bodies are almost uni-
versally compared, is pure water of a temperature of
60° Fahr.
Thus, if a cubic foot of water weigh 2.0 x, and a
cubic foot of silver weigh 20.0 x,
we should say that
silver was ten times heavier than water, or that its
specific gravity=10.0.
The specific gravities of solids (to which we shall
confine ourselves in the present place) is determined
by weighing them first in air and then in pure water,
the loss of weight occasioned by the support of the
water in the latter case, being equal to that of a mass
of the fluid of the same dimensions as the solid
itself.
The best practical instrument for taking specific
gravities for mineralogical purposes, is the Areometer,
or Nicholson's Portable Balance, which, fitted up
with weights and forceps in a small case, costs from
THE EXTERNAL CHARACTERS.
11
30s. to 35s.* This instrument is represented by fig. 1,
plate 1; it is made of brass or German silver.
A, represents the upper cup; B, the notch or index
mark (explained below) on the stem; C, the lower
cup; D, the perforated cover to the cup C, which
slides up and down, and serves to prevent the mineral
from being washed out of the cup when placed in the
water. At the point E, within the cylinder, is enclosed
a certain quantity of lead, so as to make the instru-
ment float in an upright position.
The following
method of using this instrument is reprinted from
'Practical Mineralogy,' p. 154.
First place the instrument in any convenient vessel full of
rain water (a common bed-room ewer for example).†
Secondly place the weights one by one in the upper cup,
until the notch on the stem, which supports it, be exactly on a
level with the surface of the water, and note down the amount
of weight which causes this depression (calling it A).
:
Thirdly remove the weights, and place in the cup the
mineral (the Sp. gr. of which you wish to ascertain), adding
the weights as before, until the notch on the stem again coincide
* Cheaper kinds may however be had, made of tinned iron-
plate, at as low a price as eight or nine shillings, and which
will probably answer every purpose; but having never used one
of this price, I cannot, of course, testify as to their giving cor-
rect results.
† Distilled water of a temperature of 60° Fahr. must be used
in delicate investigations, but rain water, at the common tem-
perature, is generally sufficient for practical purposes.
Broken into small fragments, if possible.
12
CHARACTERS OF MINERALS.
with the surface of the water, and note down this weight
(calling it B).
Fourthly remove the weights, and place the mineral in the
lower cup (beneath the water), again placing the weights in the
upper cup until the notch on the stem once more coincide with
the surface of the water, and note down this weight, which
will be greater than the last (calling it C).
Lastly: subtract B (the second weight) both from A and from
C, separately, and divide the greater remainder by the lesser,
when the quotient will be the specific gravity sought.
Example, referring to a crystal of LIEVRITE, from Elba.
GRS.
130.50 A
20.20 B
110.30
GRS.
47.60 C
20.20 B
27.40
27.40) 110.30 ( 4·0, &c.
109.60
700
The Sp. gr. therefore
= 4.0.
Note.-The first weight (A) ought to be always the same, and
may therefore be called the Balance or Standard Weight, and
its amount should be scratched on the cup, or on some other
part of the instrument, so as to avoid the necessity of always
taking it before commencing operations.
Also, when the mineral is removed to the lower cup, the
weights in the upper cup need not be taken away, but fresh
ones added until the notch on the stem be sunk to the level of
the water; in which case B must only be subtracted from A
(the balance weight), and the amount of these newly added
weights will be the divisor for the remainder of the sum, as a
glance at the preceding example will show. It is, however,
better perhaps to follow the first method, and to clear the cup
entirely, as it lessens the chance of error.
THE EXTERNAL CHARACTERS.
13
Streak.
(Sk.)
A simple and very effective character. It might
the more properly, perhaps, be denominated colour of
powder, as it signifies the colour of powder produced
by drawing or "streaking" a mineral across a file,
or piece of biscuit porcelain. The best way to dis-
tinguish the streak, is to take a fine file, and drawing
it once or twice across the mineral under examination,
pass it lightly over your own finger, when the colour
will be left thereon, and may be noted easily. The
shining lustre produced on some minerals, by scratch-
ing them with a sharp instrument, is also, however,
sometimes comprehended under this term.
The greater number of minerals of a non-metallic
aspect possess an uncoloured or white streak; whilst
the greater number of those possessing a metallic
aspect yield a black streak or powder; when, there-
fore, in either of these divisions, a mineral gives a
streak of a different colour, its discrimination is
greatly facilitated, and easily effected by the addition
of one or two other characters.
Thus, in minerals of a non-metallic aspect, the
following only yield a red streak, and they may be
discriminated from one another by the other charac-
ters attached.
C
14
CHARACTERS OF MINERALS.
Kermesite.-H. below 2.0; volatilizable before the blow-pipe,
leaving a white crust* on the charcoal.
Minium.-H. below 2.0; volatilizable before the blow-pipe,
leaving a yellow crust* on the charcoal.
Cinnabar.-Sp. gr. above 6.6.
Ruberite.-H.
the blow-pipe.
3.5—4·0.
Yields a bead of copper before
Proustite.-Yields a garlic-like odour before the blow-pipe on
charcoal.
Argyrythrose.-Sp. gr. 5·8—5·9.
Miargyrite.-Sp. gr. 5·2—5·4.
A
Anhydro-Ferrite (some varieties).—Magnetic after roasting,
Fusible only on the edges.
Note.- Miargyrite and Anhydro-Ferrite have generally a
metallic aspect.
Form.
(In the following article, all figures in italics refer to the illus-
trations of Chapman's Practical Mineralogy.')
(
A character (when regular) of the highest interest,
yet of limited utility in the discrimination of minerals;
for although the greater number of mineral bodies are
certainly found sometimes in a crystallized state, that
is, possessing a regular or definite form, yet they
occur far more frequently in an amorphous state, pos-
'
* This disappears in the reducing flame.-See Action of the
Blowpipe,' further on.
THE EXTERNAL CHARACTERS.
15
sessing an irregular or indefinite form; a character,
of course, utterly useless as a means of discrimina-
tion. There are, also, many minerals which have
hitherto never been found crystallized.
1. Regular Form.-It is impossible, in a brief
treatise like the present, to enter into the details of
the abstruse and complicated science of crystallogra-
phy in a very satisfactory manner; all that can be
done, therefore, is to give as clear and simplified an
account as possible of its general principles, with their
application to mineralogy.
A. Regular Form. Preliminary Remarks.—All
inorganic substances, possessing a regular or symme-
trical form, are termed "crystals," and this, whether
they be opaque or transparent.
Crystals possess, externally, planes, edges, and
angles; and, for convenience, they are supposed to
contain, internally, certain imaginary lines termed
"axes",
Planes are (apparently) level surfaces, bounded by
right lines. Where two planes meet, an edge is
formed; where three edges join, a solid angle (or
corner) is produced.
The union of planes, edges, and angles, therefore,
constitutes a regular geometrical solid, or crystal;
and if we suppose certain right lines to pass through
the exact centre of this crystal, crossing each other
at the centre, and terminating in the middle of the
16
CHARACTERS OF MINERALS.
external surfaces, edges, and solid angles, we shall
have a just idea of a system of axes.
(To illustrate this, cut out of an apple, or a piece of
cork, a small cube, and taking three pins, run one
through the centre of the cube from top to bottom,
another from left to right, and the third from back to
front; these pins will then represent three principal
axes; and others might be supposed to run diagonally,
downwards from the four top (or upwards from the
four bottom) corners-and two crossing the horizon-
tal pins on the same level, from the centres of the
alternate lateral edges, &c.)
The top and bottom planes of crystals are called
the terminal planes, or bases; the side planes
(which are generally the longest) are named lateral
planes.
A crystal is said to be truncated when some or all
of its solid angles appear as though cut off, a single
plane occurring where a point or edge should be.*
Or the part wanting, is said to be replaced by a single
plane, or simply replaced: ex. the corners of figs. 2,
9, 23.
A crystal is said to be bevelled, when some or all of
its edges, planes, or solid angles, are so altered as to
present, in the altered part, two smaller converging
planes terminating in an edge.* Or the part altered
* Werner.
THE EXTERNAL CHARACTERS.
17
is said to be replaced by two planes: ex. the edges of
figs. 6, 13, 22.
*
A crystal is said to be acuminated, when it loses
some or all of its angles or planes, presenting in their
stead, at the altered part, three or more planes con-
verging together. Or the part altered, is said to be
replaced by three or more planes, as the case may
be: ex. the planes of fig. 14, the corners of figs.
10, 11.
The following are the chief crystalline forms, with
their divisions, or chief modifications, which occur in
nature.
B. Regular Form. Forms of Crystals.
The Tetrahedron (pl. ii, fig. 1) is a solid contain-
ing four equilateral triangular faces, which incline to
each other at an angle of about 70° 32'. It has also
four solid angles, and six edges. The chief modifica-
tions of this figure are formed by the truncation or
cutting off of all the corners or solid angles at right
angles to the base, when the cube (fig. 2) is produced;
or in an oblique direction, when the regular octuhe-
dron (fig. 3) is formed.
The Hexahedron or Cube (pl. ii, fig. 2) has six
square faces, inclining to each other at an angle of 90°.
It has also eight solid angles, and twelve edges. Its
* Werner.
c 2
18
CHARACTERS OF MINERALS.
principal modifications are, the octahedron, formed by
cutting off the solid angles; the rhomboidal dodeca-
hedron, formed by truncating the solid edges, and the
tetragonal icositetrahedron (pl. ii, fig. 5), by a replace-
ment of each of the solid angles by three planes till
they join. The regular tetrahedron (fig. 1), and
numerous other modifications, may also be formed
from this solid. (See Chapman's Practical Miner-
alogy,' figs. 1 to 35).
The Regular Octahedron (pl. ii, fig. 3) possesses
eight equilateral triangular faces, inclining to each
other at an angle of 109° 28′ 16″. It has also six
solid angles, and twelve edges. The plane angles of
the triangular faces are all 60°; and the angle of
incidence of two faces over a point or solid angle,
is 70° 32'. The cube formed by cutting off the solid
angles; the rhomboidal dodecahedron (fig. 4) pro-
duced by cutting off the solid edges; the tetrahedron,
&c., are the chief modifications of this solid. (See
as above.)
The Rhomboidal Dodecahedron (pl. ii, fig. 4) has
twelve rhombic faces, inclined to each other at an
angle of 120°. The plane angles of the faces are 109°
28′ 16″, and 70° 32′ 44″. Its chief modifications are
the cube and the regular octahedron.
The Tetragonal Icositetrahedron (pl. ii, fig. 5)
possesses twenty-four similar trapezoidal faces. Its
modifications are similar to the above.
THE EXTERNAL CHARACTERS.
19
Thus, the forms represented by figs. 1, 2, 3, 4, and 5,
may be said to belong to one, or the same, system
of crystallization, as each may be derived from the
others.
The Rhombohedron (pl. ii, figs. 6 and 7) is a solid
containing six equal and similiar rhomboidal faces.
Fig. 6 represents an obtuse, fig. 7 an acute rhombo-
hedron, each of which may be formed from the
other. If a rhombohedron be placed in one of the
positions shown at fig. 8, and lines be drawn from
each of the solid angles, except the two vertical ones,
to a horizontal plane, then the connexion of these lines
by other right lines on the plane, will form a regular
hexagon as shown in the figure. This is termed the
horizontal projection of the Rhombohedron, and it
may be shown almost as well by the projection of its
shadow by candle-light. To effect this, support the
crystal or model on one of the solid angles, by holding
the opposite corner with the point of the finger, and
take care to let a solid angle be exactly facing the light,
so that its rays may fall directly upon it.
From the above, it will be perceived that the
regular hexagonal or six-sided prism (pl. ii, fig. 9)
is a modification of the rhombohedron (see "six-sided
prisms"). It has also other modifications of a
pyramidal form (pl. ii, figs. 10, 11. See also
'Practical Mineralogy,' fig. 64 to 138).
Prisms are solids which must have at least three
parallel lateral planes, and two parallel terminal planes.
20
CHARACTERS OF MINERALS.
Prisms are, however, rarely found with only three
lateral planes, but have usually four, six, eight, or
twelve; the latter numbers being apparently formed
by the truncation of lateral edges. (Examine figs. 139
and 140.)
Prisms are termed "right prisms" when their lat-
eral and terminal planes are at right angles to each
other; and "oblique prisms,” when such is not the case.
The Regular Six-sided Prism (pl. ii, fig. 9), a
modification of the rhombohedron, as stated above, is
a “right prism,” and it may be distinguished from
other six-sided* (though irregular) prisms, by the
angle across any of its vertical edges being = 120°.
The Right Square Prism (pl. ii, fig. 10) has its
terminal planes of equal measurement both ways
across, thereby forming squares, but with its lateral
planes either longer or shorter than the width of its
terminal planes. A cube cut horizontally in half, or
two cubes placed one upon another will illustrate this.
For modifications, see Chapman's 'Practical Miner-
alogy,' fig. 36 to 63a.
3
The Right Rectangular Prism (pl. ii, fig. 18) is a
right prism, with rectangular, though not square, ter-
minal planes. For modifications, see Practical
Mineralogy,' fig. 139, &c.
6
The Right Rhombic Prism (pl. ii, fig. 14) is a right
prism, with rhombic planes; that is to say, with
* Liable to an occasional exception.
THE EXTERNAL CHARACTERS.
21
lateral planes which meet together at a greater or less
angle than one of 90°. For modifications, see as
before, fig. 150, &c.
Note. The Right Rectangular, and the Right Rhombic, prisms,
are modifications of, and pass into, each other; they, therefore,
belong to the same system.
The Oblique Rectangular, and the Oblique Rhombic
Prisms, also belong to one system of crystallization.
These terms have been explained above. For modi-
fications see 'Practical Mineralogy,' fig. 162a, &c.
Doubly Oblique Prisms can scarcely be described in
an intelligible manner to the beginner, without the
aid of models. The meaning of the term, "doubly
oblique," may, however, be illustrated by a reference
to oblique prisms. Oblique prisms, if placed on a
table or plane surface, will be found to lean on one
side, or to overhang their base, in one direction ;-
doubly-oblique prisms, in the same position, will be per-
ceived to incline in two directions (see 'Practical
Mineralogy,' fig. 239, &c.)
We have now to consider the forms of pyramidal
crystals, all varieties of which are referrible to one or
the other of the above systems.
Pyramids are, geometrically speaking, solids com-
posed of one plane surface, from which rise three or
more inclined triangular faces meeting in a point,
called the "vertex," or "apex;" but, crystallogra-
phically speaking, pyramids have six or more inclined
triangular faces, meeting, in equal numbers, in two
22
CHARACTERS OF MINERALS.
opposite points. Two geometrical pyramids joined
base to base will illustrate this.
From the above, it will be seen, that the regular
octahedron (pl. ii, fig. 3) is a pyramid of four sides;
but it differs from all other pyramids in being of equal
dimensions in regard to its height, and two transverse
widths. That is to say, it has three axes, at right
angles to each other, of equal length.*
The Regular Six-sided Pyramid (pl. ii, fig. 10)
belongs to the same system of crystallization as the
rhombohedron and the regular six-sided prism, and it
may be formed from this latter solid in the same man-
ner as the regular octahedron is formed from the
cube, namely, by the deep truncation of all the solid
angles or bevelment of the edges.
In this way other pyramids may, of course, be
formed from any other prism, and the right square
prism (pl. ii, fig. 12) considered as the type of its
system of crystallization, is modified in this manner
in an extraordinary degree of frequency, so as to have
obtained for this system the name of "pyramidal."
(See further on: 'Systems of Weiss.')
Pyramidal modifications also occur very frequently
in the other systems described above, except the last.
Pyramids are said to be "perfect" if they possess
points or apices, and "imperfect" if they be trun-
* Other four-sided pyramids are frequently termed obtuse or
acute octahedrons, octahedrons with rectangular bases, &c.
THE EXTERNAL CHARACTERS.
23
cated on the apices. Prisms and pyramids are very
generally combined in the same crystal, as in fig. 45
to 64, 112 to 114, &c. ('Practical Mineralogy') for
perfect pyramids; and 38 to 44, 137a, 138, &c., for
imperfect pyramids. Pyramids are occasionally
acuminated on the apices, or the apex of a pyramid
in that case, be said to be replaced by three or
more planes. These acuminating planes are, of
course, always more obtuse than the original planes,
otherwise re-entering angles would be formed. (Figs.
58, 59, 89, 197, &c.)
may,
In like manner, if a pyramid be combined with a
prism, the terminal planes of that prism may be said
to be each replaced by three or more planes, as the
case may be.
Retrospect.
The following is a tabular view of the above sys-
tems of crystallization, with the most commonly
occurring, or best defined, individuals, belonging to
each.
Regular Tetrahedron.
Cube, or Hexahedron › Combinations of these two
1. Regular Octahedron
2.
Rhomboidal Dodecahedron.
Tetragonal Icositetrahedron.
Right Square Prism.
forms.
Obtuse Pyramids with Square Common Base.
Acute Pyramids
Combinations of Square Prisms and Pyramids.
24
CHARACTERS OF MINERALS.
Obtuse Rhombohedrons.
Acute Rhombohedrons.
3.
Regular Six-sided Prism.
4.
5.
Regular Six-sided Pyramid.
Combinations of the two latter.
Right Rectangular Prisms.
Right Rhombic Prisms.
Octahedrons with rectangular bases.
Octahedrons with rhombic bases.
Truncated modifications of these forms.
Oblique Rectangular Prisms.
Oblique Rhombic Prisms.
Pyramidal modifications of the above, with oblique
bases; and with oblique terminal planes, if imper-
fect.
6. Doubly-oblique Prisms.
C. Regular Form. Theory of Primary or Pri-
mitive Forms.—Nearly all crystallized minerals, and
those possessing a crystalline structure, may be me-
chanically divided or "cleaved" in certain definite.
directions (see "Cleavage") by means of a knife or
other sharp instrument, and the application of a
greater or less degree of force, into certain definite
forms. These forms are the solids described in the
preceding section, and they were termed "primary"
or "primitive," by the orginal founders of this crys-
tallographic doctrine, in the supposition that they
resembled the molecules or composing atoms (or germs,
as it were) of the crystals to which they belong. A
THE EXTERNAL CHARACTERS.
25
consideration of the truth or fallacy of this theory,
does not come within the limits of the present brief
treatise; but it may be remarked, that the prin-
cipal objection to it is the fact, that some minerals
may be cleaved into two or more distinct forms be-
longing to different systems of crystallization, and
that consequently, in such cases, one of these forms.
has to be selected arbitrarily, as the "primitive" one.
However, a somewhat similar fact might be ad-
vanced against the principles of crystallography it-
self, inasmuch as that many compounds of the same
elements in the same proportions crystallize under
different circumstances, in forms peculiar to different
systems.
By the term of "Primitive or Primary Form," we
are therefore to understand the form into which a
mineral may be split or cleaved, by following the
direction of certain natural joints, which it may pos-
sess; and, for a further consideration of which, we
refer the reader to the article "cleavage." Before,
however, concluding this section, it must be men-
tioned that many minerals, to which a "primary
form" has been assigned by mineralogists, have never
been cleaved into that form, but are only supposed,
from various coinciding circumstances, to be cleav-
able into it, were purer specimens to be procured, or
were our means of producing mechanical cleavage
more effective. Many of the native metals, however,
D
26
CHARACTERS OF MINERALS.
and some other minerals, appear to possess a perfectly
compact or uncleavable structure.
D. Regular Form. Systems of WEISS.-We have
shown above, that all crystalline forms are referrible
and peculiar to one of six systems, and that all the
forms belonging to any one of these systems may be
deduced or derived from each other, but that they
have no connexion with the forms of the other sys-
tems. These are the fundamental principles of the
doctrine of WEISS, and the forms belonging to each
of the six systems described above, are peculiar also to
each of the six systems of his school of crystallography;
but the specific differences of each system are founded.
on the relations of the axes of crystals to each other.
These assumed lines or axes, and their various posi-
tions, have been already explained; we have now,
therefore, to consider the relations which they bear
to each other, in the "six systems of axes of crys-
tallization" of WEISS, and his renowned follower,
ROSE.
The group of forms, numbered 1 (page 23), is the
first system of the Germans, and is named "the
Regular System." The crystals or forms belonging to
it, must have three axes, all of equal length, and
placed at right angles to each other. This system is
better known in England as the octahedral, or the
tessular, system,-the regular octahedron or the cube
being taken as its type; but the original name is far
THE EXTERNAL CHARACTERS.
27
more rigorously definite, and less liable to miscon-
ception, and therefore far better.
The group, numbered 2, is termed by ROSE, "the
Two-and-one-axed System," and the forms belonging
to it must have three axes, two of the same length,
and one of a different length (either longer or shorter),
and all placed at right angles to each other. This
system is also termed the pyramidal system, from the
constant occurrence of pyramidal combinations in its
comprised forms; but here again, for the same reasons
as the last, the original name is infinitely better.
The third group (3) is called "the Three-and-one-
axed System," and the forms composing it must have
four axes, three of equal length crossing each other
(on the same plane) at an angle of 60°, and the fourth
of a different length (longer or shorter), and placed at
right angles to the rest. The English name for this
system is the Rhombohedral system, but the Ger-
man term is certainly the more definite, and, as such,
preferable.
The fourth group (4), is termed "the One-and-
one-axed System," but it might, perhaps, the more
properly be termed "the Right unequiaxed System.”
The forms of which it is composed must have three
axes, all of different lengths, and placed at right an-
* These positions the student will easily comprehend if he
examine a crystal or model of the regular six-sided prism, and
imagine the direction of the axes as given above.
28
CHARACTERS OF MINERALS.
gles to each other. The English name for this group
is "the Prismatic system."
The fifth group (5) is called "the Two-and-one-
membered System," but it might also be termed "the
Oblique unequiaxed System." Its included forms
must have three axes of unequal lengths, two of
which cross each other obliquely, and are perpendi-
cular to the third. The English name for this group
is "the Oblique-prismatic System."
The sixth and last group (6) is named "the one-
and-one-membered System," but it might also be called
"the doubly-oblique unequiaxed System." The forms
belonging to it must have three axes, all of unequal
lengths, and all placed obliquely to each other. The
English synonym is "the doubly-oblique prismatic
System."
E. Regular Form. Method of describing Crystals.—
Before concluding our account of the "regular forms"
of mineral bodies, with a modification of Rose's
Catalogue of Crystallized Minerals, we would briefly
mention the methods of describing crystals at present
in use.
These methods are two, namely: by words
at full length, and by signs or abbreviations. The
former may be illustrated by the following descrip-
tions of the common form of quartz crystals.-(Chap-
man's 'Min.,' fig. 134.)
(1) A six-sided prism, acuminated at the terminal planes,
with six planes, the acuminating planes being set on the lateral
planes.
THE EXTERNAL CHARACTERS.
29
(2) A six-sided prism, having the terminal planes replaced
by six planes forming a six-sided pyramid.
(3) A six-sided prism, combined with a perfect six-sided
pyramid, &c.
A simple method (not before published) of describ-
ing crystals by signs, is the following:-
It consists in first marking down the number of
the system to which the crystal under examination
may belong; secondly, the chief form of that system
from which it may have been derived; and thirdly, the
modifications which this form may be supposed to have
undergone to produce the crystal under examination.
This may be done by using, for the third place, the
signs given below, and setting down, in the second
place, merely the first letter or two of the principal
form as mentioned above. Thus: I.; C.; signifies the
cube -I.; O.; the regular octahedron:-2; P. 4;
the square four-sided prism of the second system :-
3; Py. 6; the six-sided pyramid of the third system:
—4; Rh. P. 4; a rhombic four-sided prism of the
fourth system; and so on, using other abbreviations.
to express the different forms.
The signs of the modifications to be used in the
third place, are the following:
T. or t. signifies truncated; if the truncating planes be large,
the capital letter is used, and vice versa.
B. or b. signifies bevelled, the letters to be used as above.
A. or a. signifies acuminated. The number of the acuminat-
ing planes must be marked after; as, A. 6, &c.
D 2
30
CHARACTERS OF MINERALS.
Truncation, it will be remembered, expresses a
single plane; bevelment, two planes meeting in an
edge; and acumination, three or more planes meet-
ing in a point.
These letters are always to be placed above, and
separated by a line (in the manner of fractions) from
those which follow.
p. signifies planes.
e. edges.
a. solid angles.
1. lateral.
t. terminal.
+ obtuse.
acute.
If the above letters be used without any figure
being attached, the whole of the planes, angles, &c.,
are supposed to have undergone the expressed modi-
fication; otherwise, the number of the planes, &c.,
which have experienced that modification, is to be
attached. Thus:
T.
2 + l. e.
signifies, deeply truncated on the two obtuse lateral
edges.*
These few signs are sufficient to describe any
crystal, however complicated, in a neat and clear
The following examples are annexed, to
manner.
familiarize the student with the method.
* The numeral (2) might, however, be omitted in this case, as
the sign + (obtuse) is attached to the lateral edges.
THE EXTERNAL CHARACTERS.
31
:
!
The cube truncated deeply on the angles.
1; C.;
T.
a.
The regular octahedron slightly bevelled on all its
edges.
1.; O.;
b.
e.
The four-sided square prism, having its terminal
planes replaced by a large four-sided pyramid.
2; P. 4;
A. 4.
t. P.
A four-sided square obtuse pyramid, slightly trun-
cated on the vertices or terminal solid angles.
2; + Py. 4;
t.
t. a.
The letter V (vertex) may be used instead of t. a.
The regular hexahedral prism acuminated on its
terminal planes, with six planes having their common
summits deeply truncated.
A. 6; T.
3; P. 6;
t. p.; v.
An oblique four-sided rhombic prism, having its
obtuse lateral edges deeply truncated.
T.
5; Rh. P. 4;
+ 1. e.
6
Fig. 107 of Chapman's Practical Mineralogy.'
3; P. 6.
T.; A. 6; a. 6; a. 6; T.
1. e.; t. p.; V.; V.; V.
32
CHARACTERS OF MINERALS.
The above may be described, in words, as-a regu-
lar six-sided prism (belonging to the third system of
crystallization), having its lateral edges deeply trun-
cated, its terminal planes acuminated with six large
planes, these again acuminated with six small planes,
and these last also acuminated with six small planes,
having their common vertices deeply truncated.
In concluding our description of this method, we
may state, that it possesses the advantage of requiring,
when intended for press, merely the ordinary type of
the printing office.
For other methods of describing crystals by signs,
we refer the reader to complete works on Crystal-
lography, and especially to the System of Crystal-
lography' of Mr J. J. GRIFFIN, of Glasgow, a work
which we regret not to have met with before the
greater part of this section was in type, and which,
for clearness, simplicity, and correctness, we believe
to be unequalled, especially as an elementary treatise.
The price of this work is about 12s., and the London
publisher, Mr Tegg, of Fleet street.
F. Regular Form. Modification of Rose's Cata-
logue of Crystallized Minerals.-In the following
catalogue, the minerals belonging to each system will
be classed according to the arrangement adopted in
Practical Mineralogy,' Chapter III. It must be
remembered that many mineral substances which
occur in nature will not be mentioned in the present
·
THE EXTERNAL CHARACTERS.
33
classification, as they are never met with in a crys-
tallized state, or do not present a crystalline or
cleavable structure.
SYSTEM 1.
The Regular System.
Octahedral System.
Tessular System.
Native Substances.
Platinum.
Palladium.
Gold.
Silver.
Mercury.
Native amalgam.
Bismuth.
Lead.
Copper.
Iron.
Carbon (the diamond).
Arseniurets.
Smaltine.
Seleniurets.
Seleniuret of silver and lead.
Seleniuret of lead and mercury.
Clausthalite.
Seleniuret of lead and copper.
Seleniuret of lead and cobalt.
Berzeline?
Sulphurets.
Argyrose.
34
CHARACTERS OF MINERALS.
Galena.
Phillipsine.
Iron pyrites.
Koboldine.
Alabandine.
Zinc-blende.
Fahl-ore.
Hartmannite.
Cobaltine.
Simple Oxides and Acids.
'Ruberite.
Aimantine.
Franklinite.
Arsenic acid.
Titaniates.
Fyrochlore.
Chromates.
Chromoferrite.
Aluminates.
Pleonaste.
Gahnite.
Spinel.
Silicates.
Silicate of bismuth.
Ferrugino-calcareous garnet.
Ferrugino-aluminous garnet.
Manganesian garnet.
Chrome garnet.
Calcareo-aluminous garnet.
Lazulite (lapis lazuli).
Ittnerite.
Hauyne.
THE EXTERNAL CHARACTERS.
35
Analcime,
Sodalite.
Spinellane.
Borates.
Boracite.
Arseniates.
Pharmacosiderite.
Sulphates.
Soda-alum.
Alum.
Amonalum.
Fluorides.
Yttrocerite.
Fluor spar.
Chlorides.
Kerargyrite.
Rock salt.
Sal ammoniac.
SYSTEM 2.
The Two-and-one-axed System.
Pyramidal System.
Tellurets.
Elasmose.
Sulphurets.
Copper pyrites.
Simple Oxides and Acids.
Hausmannite.
Braunite.
Cassiterite.
み
​36
CHARACTERS OF MINERALS.
Rutile.
Anatase.
Columbates.
Fergusonite.
Tungstates.
Scheelitine.
Scheelite.
Molybdates.
Melinose.
Silicates.
Zircon.
Mellilite.
Gismondine?
Apophyllite.
Idocrase.
Wernerite.
Gehlenite.
Phosphates.
Uranite.
Chalkolite.
Phosphyttrite.
Fluorides.
Cryolite.
Chlorides.
Chloride of mercury.
SYSTEM 3.
The Three-and-one-axed System.
Rhombohedral System.
Native Substances.
Antimony.
:
THE EXTERNAL CHARACTERS.
37
Arsenic.
Tellurium.
Arseniurets.
Nickeline.
Tellurets.
Bornine?
Sulphurets.
Cinnabar.
Magnetic Iron Pyrites.
Capillose.
Molybdenite.
Argyrythrose.
Polybasite.
Proustite.
Carburets.
Graphite.
Simple Oxides and Acids.
Anhydro-Ferrite.
Corundum.
Quartz.
Titaniates.
Titanio-Ferrite.
Chrichtonite.
Vanadiates.
Johnstonite.
Silicates.
Dioptase.
Cronstedite.
Pyrodmalite.
Cerite.
Eudyalite.
Talc.
E
38
CHARACTERS OF MINERALS.
Chlorite.
Emerald.
Mica: some varieties.
Davyne.
Chabasite.
Levyne.
Gmelinite.
Nepheline.
Pinite.
Tourmaline.
Phosphates.
Pyromorphite.
Apatite.
Arseniates.
Mimetese.
Euchlorose.
Sulphates.
Alumstone.
Carbonates.
Siderose.
Manganese Spar.
Smithsonite.
Breunnerite.
Magneso-Calcite.
Ankerite.
Calcite.
Nitrates.
Nitrate of Soda.
Fluorides.
Flucerine.
THE EXTERNAL CHARACTERS.
39
SYSTEM 4.
The One-and-one-axed System.
The Right unequiaxed System.-CHAPMAN.
Prismatic System.
Native Substances.
Osm-Iridium.
Sulphur.
Antimoniurets.
Discrase.
Arseniurets.
Mohsine.
Tellurets.
Sylvane.
Mullerine.
Sulphurets.
Stromeyerine.
Sternbergite.
Bismuthine.
Aikinite.
Chalkosine.
Radiated Iron Pyrites.
Stibine.
Orpiment.
Psaturose.
Donacargyrite.
Zinkenite.
Jamesonite.
Bournonite,
Berthierite.
Mispickel.
Simple Oxides and Acids.
Hydro-Ferrite.
Pyrolusite.
40
CHARACTERS OF MINERALS.
Manganite.
Spartalite.
Brookite.
Exitelite.
Kermesite.
Columbates.
Columbite.
Aluminates.
Chrysoberyl.
Silicates.
Lievrite.
Electro-Calamine.
Chrysolite.
Picrosmine.
Andalousite.
Chiastolite.
Staurolite.
Iolite.
Pyrophyllite?
Prehnite.
Stilbite.
Epistilbite.
Comptonite.
Thomsonite.
Phillipsite.
Nuttalite?
Glaucolite?
Harmatome,
Elaolite?
Spodumene?
Killinite ?
Topaz.
Pycnite.
Phosphates.
Apherese, or Libethenite.
THE EXTERNAL CHARACTERS.
41
Triplite.
Wavellite.
Childrenite.
Klaprothine.
Amblygonite.
Arseniates.
Olivenite.
Euchroite.
Leirochroite.
Liroconite.
Scorodite.
Haidingerite.
Sulphates.
Anglesite.
Brochantite.
Konigine.
Gallitzinite.
Epsomite.
Polyhallite.
Anhydrite.
Celestine.
Barytine.
Thenardite.
Apthalose.
Carbonates.
Lead Spar.
Caledonite.
Arragonite.
Strontianite.
Witherite.
Nitrates.
Nitre.
Fluorides.
Fluellite.
E 2
42
CHARACTERS OF MINERALS.
Chlorides.
Mendipite.
Matlockite.
Atakamite.
SYSTEM 5.
The Two-and-one-membered System.
The Oblique unequiaxed System.-CHAPMAN.
Oblique Prismatic System.
Sulphurets.
Realgar.
Miargyrite.
Plagionite.
Titaniates.
Æschynite.
Tungstates.
Wolfram.
Chromates.
Crocoisite.
Vauquelinite.
Silicates.
Achmite.
Gadolinite.
Bronzite.
Anthophyllite.
Hypersthene.
Augite.
Hornblende.
Wollastonite.
Sillimanite.
Fahlunite.
Epidote.
Euclase.
THE EXTERNAL CHARACTERS.
43
Mica: some varieties.
Zoizite.
Heulandite.
Laumonite.
Scolezite.
Brewsterite.
Mesotype.
Feldspar.
Borates.
Borax.
Datholite.
Phosphates.
Ypoleime, or Rhenite.
Vivianite.
Triphyline.
Heterosite.
Hureaulite.
Wagnerite.
Arseniates.
Aphanese.
Erythrine.
Pharmacolite.
Sulphates.
Cupreous Sulphate of Lead.
Melantherite.
Botryogene.
Rhodhalose.
Johannite.
Gypsum.
Glauberite.
Exanthalose.
Carbonates.
Leadhillite.
Lanarkite.
44
CHARACTERS OF MINERALS.
Cuprazurite.
Malachite.
Baryto-Calcite.
Gaylussite.
Natron.
Trona.
SYSTEM 6.
The One-and-one-membered System.
The Doubly-oblique unequiaxed System.-CHAPMAN.
Doubly Oblique Prismatic System.
Simple Oxides and Acids.
Diaspore.
Sassoline.
Silicates.
Rhodonite?
Babingtonite.
Kyanite.
Axinite.
Labradorite.
Anorthite.
Latrobite.
Couseranite.
Albite.
Pericline.
Petalite.
Sulphates.
Cyanhalose.
THE EXTERNAL CHARACTERS.
44*
In conclusion, we have to remark that certain
substances occasionally occur in double forms, in
which case two or more of their crystals are united
under certain definite laws, forming of course re-
entering angles. These double crystals (which must
not be confounded with implicated, grouped, or ad-
hering crystallizations) are termed twin, macled,* or
cross crystals, and the following minerals are those
which principally exhibit them: harmatome, stauro-
lite, arragonite, feldspar, albite, augite, hornblende,
spinel, gahnite, cassiterite, radiated iron pyrites,
copper pyrites, and bournonite.
Finally, it should be mentioned that there occur in nature,
though rarely, certain crystals, formed (if it may be so ex-
pressed) in a manner contrary to the laws of regular crystalliza-
tion. Thus, in Cornwall, we have cassiterite (ox. of tin),
assuming the form of feldspar, and wolfram that of scheelite
(tungstate of lime). These crystals, which are usually rough
and ill-formed, are termed false, pseudomorphic, or spurious
crystals, and appear to be produced in one, or perhaps both of
the following ways, as promulgated by WERNER-viz.: first,
when genuine crystals, becoming incrusted with foreign matter,
decay, and leave the incrustation exhibiting their form, though
hollow within, as pseudo-morphic crystals sometimes are; and
secondly, when true imbedded crystals decay in course of time,
and the spaces become filled up with matter of a different
* Masclé, an old French term, formerly used in armoury, to
signify the angularly-jointed pieces of metal covering the
elbows, &c.
45*
CHARACTERS OF MINERALS.
nature-or this foreign matter may perhaps act on a true and
sound crystal, destroying it (but without affecting the sur-
rounding matrix), and mixing up with it, so as to form a sub-
stance of a totally different chemical composition.
2. Irregular Form.-The irregular forms which
minerals assume are of little use in their discrimina-
tion; they will, therefore, be but briefly adverted to.
The term massive or amorphous, is applied to perfectly inde-
finite shapes. When in numerous small masses, the mineral is
said to be disseminated.
Of rounded forms, the following may be mentioned: botryoidal,
reniform, mamillated, or blistered, composed of globular elevations
and depressions, ex. varieties of copper pyrites, ox. of iron,
calcedony; globular or nodular, occurring in rounded pieces,
ex. flint; amygdaloidal, in flat elliptical pieces, ex. many zeolitic
minerals, calc-spar, &c.; and liquiform, composed of several
rounded masses adhering together, ex. varieties of galena.
Elongated forms may be: dentiform, resembling pointed teeth,
ex. N.silver; filliform or capilliform, resembling thin wire, straight
or twisted, ex. N. silver, gold, argyrose; retiform, in thin threads
crossing each other, so as to resemble network, ex. N. silver;
dendritic, resembling fir-trees or branches, arising from groups
of minute crystals, ex. N. silver, N. copper; coralliform, re-
sembling coral, ex. arragonite; stalactitic, resembling stalac
tites, an elongated form, with (generally) a botryoidal surface,
ex. calcedony, calc-spar, ox. of iron; tubuliform, in tube-like
pieces, ex. ox. of iron, &c. Other forms are sometimes men-
tioned by authors, but, like the above, they are very vague, and
pass into each other.
Massive specimens are also found in flat pieces, and in very
flat pieces or laminæ. Also in perforated, spongiform, cellular,
and vesicular masses.
THE EXTERNAL CHARACTERS.
45
Structure and Cleavage.
The "structure" of minerals is the mode of aggre-
gation of the particles of which they are composed.
By some authors it is termed "the distinct concretions
of minerals ;" and, by WERNER, it was designated as
their "foliated fracture.”
Lamellar structure is composed of broad distinct
concretions of about equal length and breadth. If
these concretions extend evenly through their entire
length, the structure is said to be "perfectly lamellar;"
if otherwise," imperfectly lamellar." When the con-
cretions are very thin, the structure is termed laminar
or foliated, and it may be either straight or curved.
Feldspar and pure varieties of barytine are examples
of lamellar structure, and mica, talc, &c., are exam-
ples of laminar concretions.
Prismatic or Bladed structure consists of long and
rather narrow concretions, forming a transition from
the lamellar into the fibrous structure.
These concre-
tions may be straight or curved, and disposed in a
regular or confused manner. The term "bladed" is
applied to the concretions when flat or thin, as in
Kyanite, &c. Examples of "prismatic" structure
will be found in amethyst quartz, in certain varieties
of barytine, apatite, arragonite, and other minerals.
Fibrous structure consists of fibrous, or very thin
and capillary, concretions, either straight or curved,
46
CHARACTERS OF MINERALS.
and disposed in a parallel, radiated, or confused man-
ner. Examples of "parallel," "radiated," and "con-
fused" fibrous structure, may be found in actynolitic
hornblende; of" radiated" structure, also, in stilbite,
wavellite, and numerous other minerals.
Granular structure is composed of minute or small
concretions, having a nearly equal length, breadth,
and thickness. It is sometimes divided into coarse
and fine granular; examples of both of which kinds
may be seen in "primitive limestone" or marble;
also in galena, &c.
Compact structure is devoid of any distinct concre-
tions, and appears to consist of one compact mass.
Examples: native gold, silver, copper, and most of
the native metals; also chalk, crysocolla, &c.
Most minerals which possess the three first kinds
of structure, and particularly those possessing the first
kind, have also certain structural lines or planes run-
ning through them in different and opposite directions,
parallel to which they may be split or "cleaved,"-
the surfaces produced by the "cleavage" being more
or less smooth and polished. These lines or planes
are termed "cleavage planes," and from the form
produced in, or cut out of, any mineral, by following
their directions, has been deduced the doctrine of
primary or primitive forms," as explained under the
article "Form," section C.
66
Some minerals may be cleaved into definite forms
THE EXTERNAL CHARACTERS.
47
with extreme facility, others yield only with the great-
est difficulty to the edge of the chisel or cutting
pliers. Calcareous spar, for instance, breaks with a
slight blow of a hammer into numerous rhombs, and
most varieties of galena into small cubes. In some
few minerals which possess only traces of cleavage,
the "primary form" has been discovered by cutting
them very thin, and holding them at night before the
strong light of a lamp or candle, so as to perceive the
directions of their structural lines; from the meeting
of two of which the positions of the others may be
generally deduced.
Surface.
The surfaces of minerals may be either uneven, gra-
nulated, rough, smooth, drusy (coated with a number
of minute crystals*), or streaked. Streaked or striated
surfaces are divided into simply and doubly streaked.
Simply streaked consists of striæ running in one direc-
tion; and doubly streaked, of striæ running in vari-
ous directions.
Simply streaked surfaces may be either longitu-
dinally streaked, the striæ being parallel with the
greatest length, or the length of the lateral planes:
ex. topaz, bismuthine, zinkenite; transversely streaked,
*Of the same substance or composition as the mineral itself.
-7
48
CHARACTERS OF MINERALS.
the striæ running across, or at right angles to the
length of the lateral planes: ex. rock crystal; dia-
gonally streaked, the striæ being parallel with the
diagonal of the planes: ex. some garnets; or alter-
nately streaked, the transverse and longitudinal striæ
occurring on alternate planes: ex. some cubical crys-
tals of iron pyrites.
Doubly-streaked surfaces may be either plumi-
formly streaked, the striæ occurring in the form of a
feather: ex. some varieties of native bismuth; reti-
cularly streaked, the striæ crossing each other either
at right angles or obliquely, forming a kind of net-
work ex. cobaltine; or scallop-formly streaked, the
striæ running in a zig-zag or waved direction: ex.
amethyst quartz.
:
It must be mentioned, that streaked surfaces often
arise from a close fibrous structure, or otherwise in-
dicate the direction of cleavage planes.
Tenacity.
This term expresses the relative mobility and co-
hesion of the component particles of mineral bodies.
It is a character of considerable importance in many
The different degrees of tenacity are the fol-
cases.
lowing:-
Brittle, possessed by minerals which grate under
THE EXTERNAL CHARACTERS.
49
the knife, and fly off in the form of powder when
attempted to be cnt: ex. quartz, feldspar, iron pyrites,
&c. Brittle minerals, or metallic globules, also break
into powder, when placed on a small anvil and struck
by the hammer.
Sectile, possessed by minerals which yield in a great
degree to the knife, without noise, the particles re-
maining on its blade: ex. galena, native bismuth,
chalkosine, talc. Sectile minerals also crush into
powder under the hammer.
Malleable or ductile possessed by minerals which
may be cut by the knife, and which flatten into span-
gles under the hammer: ex. native gold, silver, cop-
per, &c.; also argyrose and other minerals.
Transparency.
The degrees of transparency or transmission of
light, as possessed by minerals, are the following:-
:
0. Opaque, or devoid of transparency ex. Chalk, and all
minerals of a true metallic aspect.
1. Translucent on the edges: ex. Cerite, Gadolinite.
2. Translucent: ex. Feldspar.
3. Semi-transparent: ex. Calcedonic Quartz.
4. Transparent: ex. Rock Crystal, pure Calc-spar, &c.
The whole of the above terms explain themselves.
The numerals attached to each degree are sometimes
F
50
CHARACTERS OF MINERALS.
employed instead of the words at full length, to denote
the various degrees of transparency possessed by
minerals.
Note.-Transparent minerals are either singly-refracting or
doubly-refracting, presenting, in the latter case, a double view of
any thin object (such as a pin or ruled line) over which they
may be placed. Transparent calc-spar, and particularly the
limpid variety from Iceland, is well known to possess and show
very distinctly this curious property, which is, without doubt,
intimately connected with the crystalline structure of minerals.
For a further consideration of this subject, we refer those rea-
ders who may wish to follow it up to complete treatises on
optics.
Degree of Lustre.
This character is totally distinct from the Kind of
Lustre, or Aspect of Minerals, and of very inferior
consequence. It bears the same relation to trans-
parency as reflected does to refracted light.
The degrees of lustre are the following, the numerals
attached to each degree being sometimes made use of,
in the same manner as those attached to the degrees
of transparency described above.
0. Dull, devoid of lustre : ex. Chalk, Fuller's Earth.
1. Glimmering: ex. Massive Chlorite.
2. Glistening, or weakly shining: ex. Native Arsenic.
3. Shining: ex. Rock Crystal.
4. Splendent, or strongly shining: ex. Galena (most varieties).
These terms sufficiently explain themselves. The
THE EXTERNAL CHARACTERS.
51
external and internal lustre of minerals is often very
different: thus, Idocrase is splendent externally, and
but weakly shining internally,-Gadolinite, dull ex-
ternally, and shining internally. This character is,
however, of no very great utility.
Fracture.
A character, also, of subordinate importance. It is
the appearance of the surfaces produced on breaking
a mineral in any direction, except in that of its na-
tural joints or cleavage planes, which ought to be
always smooth and more or less shining.
The different appearances of fractured surfaces are
the following:-
Even: ex. basanite, a var. of quartz; slaty: ex.
common roofing slate; conchoidal, presenting convex
and concave depressions and elevations, usually ac-
companied with concentric wrinkles, as in numerous
shells, from whence the name is derived. This kind
of fracture is generally combined with a vitreous as-
pect ex. quartz, obsidian, gadolinite; uneven or
indented: ex. iron pyrites, &c.; hackly, presenting
numerous sharp and jagged points, a fracture peculiar
to the native metals: ex. copper, silver, &c. Earthy,
is merely a fine-grained, uneven fracture, joined to a
very weak or dull lustre: ex. chalk.
52
CHARACTERS OF MINERALS.
Form of Fragments.
This refers to the shapes of the small masses or
fragments produced by striking any mineral sharply
with the hammer.
These forms are usually divided into regular and
irregular shapes, but the former are bounded by
cleavage planes, and are described in the article
Cleavage, as the small cubes of galena, &c. They
are, in fact, "primary or primitive forms," and have
therefore been described before.
The irregular fragments are: cuneiform, splintery,
tabular, blunt-edged angular, and sharp-edged angular.
These terms need no further consideration, as the
character is very unimportant, and of little or no use
in the discrimination of minerals.
Frangibility.
This term comprises the relative degrees of cohesion
of the particles of minerals, but differs both from
hardness and tenacity. In trying the frangibility of
minerals, we attempt to break them, either with the
fingers or the hammer. Minerals may be either very
easily frangible, as laumonite; easily frangible, as
the common varieties of galena: or difficultly fran-
gible or tough, as hornblende.
THE EXTERNAL CHARACTERS.
53
Flexibility.
A character possessed by very few minerals, but
still, as such, of use in their discrimination. Mine-
rals may be either simply flexible, as talc, chlorite,
molybdenite, and thin pieces of selenite; or elastically
flexible, as mica-springing back when bent, to their
original positions.
Touch.
This character, of little importance, expresses the
sensation which some minerals impart to the touch.
This sensation may be either very greasy, ex. talc;
greasy, ex. steatite; rather greasy, ex. asbestus; or
meagre, ex. chalk. The sensation of a greater or less
degree of cold depends upon the high or low specific
gravity of minerals.
Soiling.
A character chiefly possessed by decomposed, or
impure, varieties of minerals, but appertaining also to
some few perfect specimens. All minerals which soil
or stain are, of course, more or less friable, or com-
posed of loosely-cohering particles. The reader will
find the greater part of these minerals (those pos-
F 2
54
CHARACTERS OF MINERALS.
sessing a non-metallic aspect) grouped together at
page 28 of 'Practical Mineralogy.'
Odour.
This character is confined to a very few minerals.
Some emit naturally a degree of odour, which is either
bituminous, as in mineral pitch, or very faintly sul-
phureous, as in native sulphur. In others, odour is
produced by breathing strongly on them, in which
case it is similar to that of clay, but this is a very in-
definite character. Odour is also produced in some
minerals by friction; thus, two pieces of quartz rubbed
together emit an empyreumatic odour; iron pyrites,
when struck by the hammer, yield a sulphureous
odour; and arsenic pyrites or mispickel an alliaceous
(garlic-like) odour. Finally, odour is developed in
some minerals by the application of heat; but this will
be treated of in describing the Use of the Blowpipe,
which see.
Sound.
A character of scarcely any use.
Rock crystal and
some other minerals (particularly if of a long and thin
shape) emit, when struck, a ringing sound. Native
amalgam, on being pressed between the fingers, or cut
with a knife, gives out a creaking sound.
THE EXTERNAL CHARACTERS.
55
Adhesion to the Tongue.
A character possessed only by such minerals as
freely imbibe moisture: ex. keffekil or meerschaum,
lithomarge, &c. This character is common to almost
all earthy mechanical mixtures and decomposed spe-
cimens.
Taste.
A confined yet very characteristic property, pos-
sessed by such minerals as are soluble in water.
It may be either saline, as in rock salt; sweetish-
astringent, as in alum; stypic and metallic, as in
melantherite; bitter, as in Epsomite; cooling, as in
nitre; pungent and alkaline, as in natron; urinous, as
in sal ammoniac; or acid, as in sulphuric acid.
Magnetism.
This character, though of limited application, is in
many cases a very important one. To try if a mine-
ral possess the property of magnetism, a small mag-
netic needle, with its centre to turn on, is necessary ;
and this little apparatus may be purchased at the opti-
cian's for about three shillings, in a thin ivory case.
not much larger than a thick pencil, and especially
adapted for the purposes of the travelling minera-
56
CHARACTERS OF MINERALS.
logist. The only metals which attract the magnet are,
iron, nickel, and cobalt; and there are very few mi-
nerals which affect it in their natural state, but many
do so after exposure to the action of the blowpipe.
All minerals which attract the magnet act equally
on both poles, with the exception of one-the aiman-
tine or magnetic oxide of iron, which attracts one
pole and repels the other. This magnetic property is
termed "polarity," and it may be always observed
by bringing two magnets together, when the cor-
responding poles will immediately repel each other;
but the north pole of one will attract the south pole of
the other, and vice versa. The aimantine being a
natural magnet, possesses therefore, of course, this
property.
Electricity.
To observe whether a mineral possess this cha-
racter or not, a small instrument, termed "an elec-
trometer” (pl. I, fig. 2), is necessary; we will, there-
fore, describe this instrument, and the method of
using it, before entering into a consideration of the
character of electricity, as possessed by minerals.
A (pl. I, fig. 2) is a stem or support of brass, ter-
minating in a fine point, upon which plays a thin
brass wire, with a centre, and having at each end a
THE EXTERNAL CHARACTERS.
57
small pith ball, B. C represents a small glass cap-
sule, upon which the instrument must be placed so as
to be "insulated," before being used.
Electricity is of two kinds : positive and negative,
or vitreous and resinous, as these kinds were formerly
termed; the one being excited by the friction of
smooth glass, and the other by that of sealing-wax,
amber, or any other resinous substance.
Like electricities mutually repel, unlike mutually
attract, each other. Thus, two bodies, both vitreously
or both resinously electrified, repel each other; but
two bodies, one vitreously and the other resinously
electrified, attract each other.
Electricity is produced in minerals either by heat
or friction, and occasionally by the mere pressure of
the fingers, as in limpid calcareous spar.
To try if a mineral possess the property of elec-
tricity, first rub it briskly for a few minutes with a
woollen cloth, and then present it to one of the pith
balls of the electrometer; secondly, heat it gently
through, and do the same; if in either case, or both
cases, it attract the ball, then it possesses electricity,
and the more strongly, the greater the distance at
which it affects it.
66
Having thus discovered that a mineral possesses
electricity," we next seek to discover which of the
two kinds this electricity may be, and for that pur-
pose proceed as follows:-
58
CHARACTERS OF MINERALS.
First, let the electrometer be insulated, by being
placed on a support of glass, or sealing-wax.
Secondly, excite a glass tube by friction, and
placing one finger on the brass stem of the instru-
ment, hold the excited tube near one of the pith balls
for a short time. Then remove the finger, and after-
wards the glass tube. The ball will now be vitreously
or positively electrified: and if an excited mineral
repel it, on being brought near, the mineral will be
known to possess the same kind of electricity, as like
electricities repel each other; but if it attract the ball,
then it will possess the resinous or negative elec-
tricity. A stick of sealing-wax may be used, of
course, instead of the glass tube, but in that case the
operator must remember that the ball will be negatively
electrified.
I have given the above description, as electrometers
(or more properly, electroscopes) of this form, having
brass supports, are usually found in mineralogical or
blowpipe cases, as fitted up at the instrument makers'.
A more simple, and, at the same time, a superior
support, may be made out of a piece of narrow glass
tube, by drawing out one end in the flame of the
spirit lamp to a fine point (on which the needle is to
play), and by inserting the other end into a piece of
cork, so as to form a secure stand for the insulated
apparatus, in using which the intervention of the left
hand is of course unnecessary.
THE EXTERNAL CHARACTERS.
59
A still simpler electroscope may be formed by
passing through a small pith or cork ball (made as
light as possible) a very thin silken thread, or if pro-
curable, a fibre of raw silk, which being, when per-
fectly dry (like the glass stem described above) a non-
conductor, it has only to be attached to any convenient
support, so as to let the ball hang freely. If this ball
be now electrified by an excited tube of glass or
sealing-wax, it will be repelled or attracted by sub-
stances positively or negatively electrified, as before
explained. Should the operator not have a piece of
pith or cork at hand, a fragment of paper or a small
feather may be made use of, but they must be pre-
viously well dried. *
In conclusion, we have to remark, that crystallized
minerals excited by heat generally possess at their
extremities, or on opposite planes, different kinds of
electricity-as the tourmaline, topaz, boracite, &c.
* A simple experiment with this easily-formed instrument
will illustrate the fact that like electricities repel each other.
Stick a pin horizontally into the wall (in a corner of the room
free from currents of air), and attach to it the silken thread
with its appendage. Then bring a stick of excited sealing-
wax near the ball or paper, and observe that this will be imme-
diately attracted to it. After a moment, remove the sealing-
wax, and again bring it near; the ball or paper will now be
repelled, and cling to the wall, having become possessed, by the
former operation, of a portion of the electricity of the excited
wax.
60
CHARACTERS OF MINERALS.
Phosphorescence.
This is the property, possessed by some few
minerals, of emitting, by heat or friction, a faint light.
It is, however, a very uncertain character, as there
are varieties of the same substance which do and do
not possess it, or rather, in which it can and cannot be
developed.
If two pieces of quartz, or of some varieties of zinc-
blende or calc-spar, be rubbed strongly together in the
dark, they will present, on the rubbed surface, a
luminous appearance. Most varieties of fluor-spar,
apatite, wavellite, and a few other minerals, give out
pale purplish or greenish phosphorescent light when
placed on a live coal, or when heated in a small test
tube over the spirit lamp, which latter process has
the advantage of retaining decrepitating substances,
as fluor-spar.
Minerals which become phosphorescent by heat
will be found to contain almost invariably either
fluorine, chlorine, phosphoric acid, boracic acid, or
the salts of baryta, strontia, lime, or zinc. Phos-
phorescence is intimately connected with the subject
of "coloured flames,” which will be treated of in de-
scribing the uses of the blowpipe.
THE CHEMICAL CHARACTERS.
61
THE CHEMICAL CHARACTERS OF MINERALS.
THESE characters are the effects produced on minerals
by the action of acids and of the blowpipe, and com-
prehend, in an extended sense, their qualitative ana-
lysis. The complete, or quantitative, analysis of
minerals, although of course essentially a "chemical
character," or a producer of "chemical characters,"
is scarcely within the province of the general mine-
ralogist, in whom a perfect knowledge of all the ab-
struse processes of chemistry is never expected. The
solubility of minerals in water, is also a "chemical
character;" but as all soluble minerals possess a taste,
this character is described amongst the physical cha-
racters of minerals above.
Action of Acids.
The effects produced on minerals by the action of
acids are effervescence, solubility, partial solubility
producing a gelatinous mass, &c. To develop these
effects, the mineral should be reduced to powder, and
placed in a small test-tube or other vessel, and the
acid, either pure or diluted, must then be gently
poured over it. The application of heat is sometimes
necessary, in which case a spirit lamp is made use of,
and the mineral and acid supported over it in a test-
tube, watch-glass, or small capsule of Berlin porcelain,
or of platinum, by means of a thin bent wire.
The lamp, when not in use, should have a small
G
62
CHARACTERS OF MINERALS.
glass cap fitted over it, to prevent the spirit from
evaporating, as shown at fig. 3, pl. I. A lamp of this
kind may be purchased for a shilling, or it may be
made by procuring a small short bottle, and passing
a narrow piece of glass tubing through the cork, to
form a neck for the wick. The cap may be made out
of a piece of wider tube, stopped at one end by hold-
ing it in the flame till the sides converge. The
spirit should never be allowed to get hot.
The acids chiefly used are: Nitric acid, Hydro-
chloric (or Muriatic) acid, and Sulphuric acid. These
must be kept in bottles, with glass stoppers and caps,
as their fumes soon destroy cork. It may not be un-
necessary to remind the beginner that these acids are
highly deleterious, destroying the clothes, &c., if
dropped upon them, and strongly staining the hands.
They should, therefore, be kept locked up, and out of
the reach of servants and inexperienced persons.
Description, Manipulation, and Action of the Blow-
pipe, and of its accompanying Apparatus.
By means of the blowpipe, and the flame of a lamp
or common candle, we are enabled to expose a small
fragment of any substance to a degree of heat as
intense as that of a furnace. Blowpipe operations,
besides their rapid execution, have, moreover, the ad-
vantage (over those of the furnace) of concealing
THE CHEMICAL CHARACTERS.
63
nothing from the operator, every change in the frag-
ment experimented upon being at once exposed to
view.
A. Description of the Blowpipe.-The blowpipe, in
its most simple form, is a narrow tube of glass or
metal, having one extremity bent round at right.
angles to the stem, and terminating in a point with a
very fine orifice. This form of blowpipe has the dis-
advantage of letting the water formed by the con-
densed breath, after using it for a short time, be blown
out into the flame, thereby causing a certain interrup-
tion or inconvenience. This disadvantage is best
remedied by having a chamber or space below the
bent part of the tube, into which the condensed
breath flows, and remains, without occasioning any
inconvenience, during the longest operation. The
blowpipes represented by figs. 5 and 6 are of this im-
proved form, and the reader will find various other
kinds figured in the catalogues of the chemical in-
strument makers, but which we refrain from describ-
ing here, as they possess no greater advantages, and
are merely modifications of the same instrument.
Fig. 7 is another form of blowpipe, exceedingly useful
on account of its portability, as, when closed, it does
not exceed a pencil-case in size. We proceed to
describe these three blowpipes separately.
Fig. 5 is called "Black's Blowpipe.".
A is a
* From having been first brought into notice by Dr Black,
64
CHARACTERS OF MINERALS.
tube of japanned tinned iron plate, about seven or
eight inches long, according to the convenience and
sight of the operator. B is a narrow tube of brass,
either soldered or fitting tightly at right angles into
the stem A, at about half an inch from its lower and
wider extremity. C is a moveable nozzle of brass or
platinum, having a very fine and perfectly round
orifice. This blowpipe may be purchased (with a
brass nozzle) for a shilling or eighteenpence; and the
large tube being made of tinned iron, it does not give
out any disagreeable odour of verdigris, such as the
brass tubes are very liable to do after a few months'
use. In point of power, this blowpipe is also equal, if
not superior, to any other kind.
Fig. 6 represents "Gahn's or Berzelius's Blow-
pipe." A is the stem (usually furnished with an
ivory or horn mouthpiece); B the reservoir to hold
the condensed breath; C the short tube (about an
inch and a half or two inches long), fitting at right
angles into the reservoir; and D the small nozzle or
jet. This blowpipe is usually made of silver or brass,
and costs, if of the former material, about twenty-five
shillings; or, if formed of brass, about six or seven
shillings cheaper sorts may, however, be had, but
they are scarcely to be recommended. The small
nozzles, both of this and the preceding blowpipe,
should, if possible, be made of platinum, as, when
soiled, which they are almost certain to be every third
or fourth time the blowpipe is used, they may be in-
THE CHEMICAL CHARACTERS.
65
stantly rendered bright and clean again by heating
them to redness on a piece of charcoal.
These nozzles cost half-a-crown each, and when sold
they have generally an exceedingly minute orifice,
which must be carefully enlarged with the point of a
fine needle, so as to make it perfectly round and
smooth; and this must be particularly attended to, or
good results will never be obtained. If the orifice
should become misshapen or too large, the nozzle
must be placed (point upwards) on a small anvil, and
struck two or three times gently with the hammer, so
as to close it again, after which it may be re-shaped
with the needle. The proper size of the orifice may
be known from the following remarks: if too small,
the whole of the flame will not be thrown out of its
vertical position (see further on); and if too large, it
will be ragged, and make a roaring noise, or appear
to have a hole through its centre.
Fig. 7 is the blowpipe invented by Dr Wollaston.
It is usually made of brass, and consists of three
pieces, which (when not in use) slip one within the
other, as shown at fig. 8, so as to be conveniently
carried in the waistcoat pocket. When soiled, the
orifice must be cleaned with a fine needle; and after
being used, it should always be wiped whilst still
warm, as the grease and dirt have then not time to
harden. The price of a well-made brass blowpipe of
this kind is about six shillings.
G 2
66
CHARACTERS OF MINERALS.
B. Of the Combustible for the Blowpipe flame.-
This may either be a common tallow candle, a wax
candle, or olive oil in a lamp with a flat wick. Com-
mon gas is also occasionally used, but it is not superior
to the flame of a good lamp, and can of course only
be employed in particular places, where a gas-pipe
may chance to be laid on. Of these combustibles the
beginner will find a candle to be the most convenient,
as it can be used in a moment without any previous
preparation; whereas the lamp requires a little ma-
nagement before it can be made to burn clearly and
steadily, and does not, besides, possess the portability
of the candle. Wax candles are infinitely superior to
tallow, as they yield a clearer and stronger flame, last
longer, and do not soil, or communicate when handled,
any disagreeable odour. The wicks of candles must
be snuffed as short as possible, without lowering or
weakening the flame, and bent slightly to the left of
the operator, or away from the inserted nozzle of the
blowpipe, supposing him to hold that instrument
always in his right hand. (See § C.)
The use of candles with the blowpipe has this dis-
advantage, namely that in using charcoal as a sup-
port for the assay (see § E and § F), the radiant heat.
from its surface causes the wax or tallow to gutter
over, and burn away very rapidly-a circumstance of
course prevented by the use of a lamp. This may,
however, be remedied in a degree by using only small
20
THE CHEMICAL CHARACTERS.
67
pieces of charcoal, when, except in some difficult
cases of reduction (see § I, 2), the above inconvenience
will scarcely be felt. In simple trials of fusibility,
&c., the wax candle is quite sufficient; and for some
operations, as the production of coloured flames (see
§ I, 5), it is superior to the lamp.
The best form of lamp is that shown at fig. 11. It
is the invention of BERZELIUs, and is termed "Ber-
zelius's blowpipe lamp." B is the body of the lamp,
of an oval form, four inches long and one inch wide,
and made of tinned iron, painted and varnished, or
japanned, on the outside. C is a brass projecting
piece and cap, the cap screwing on the inside of the
projecting piece, and being furnished with a collar of
leather (previously soaked in melted wax), which
presses tightly on its rim when screwed home, and
prevents effectually the escape of any oil from the
lamp during journeys. Within the projecting piece
is a flat wick-holder, three quarters of an inch across,
made of tinned iron plate. A is the supporting stem
for this lamp, and consists of two thin brass rods (each
about five inches long) screwing together, and fitting
also at one end, by screwing, into two cross pieces of
metal (usually bronze or brass), as represented by
D D. The lamp is connected to the stem A by a
small cylinder of tinned iron soldered to its back, and
which retains its hold on the stem either by simple
friction or by means of a screw.
68
CHARACTERS OF MINERALS.
When packed for travelling, or in the blowpipe case,
the two flat pieces (composing the foot) are placed
one above the other, and the two thin rods (forming
the stem) will then lie side by side on the upper one,
when the whole may be tied together, and placed in
one compartment of the box, the cylindrical body of
the lamp fitting into another division. The price of a
lamp of the above description varies from six to ten
shillings, but cheaper kinds, with a support and foot
of wood, not adapted for travelling, may be had for
two shillings.
C. Method of using the Blowpipe.-The effect in-
tended to be produced in using the blowpipe is to
force through it from the mouth a continual stream
of air of several minutes' duration, or for as long a
time as it may be necessary to sustain the blast.
This to beginners is always a difficult and troublesome
operation, but one, however, that requires merely a
little patience and perseverance to be thoroughly over-
come in the course of two or three days. Before at-
tempting to use the blowpipe, the following observations
are to be borne in mind-namely, that a very strong
blast is not required, and prevents the breath from
being properly economized-the common fault of be-
ginners being to blow too impetuously; and secondly,
that the stream of air is not to be forced directly from
the lungs, as such would be injurious, and soon exhaust
the operator, but that the mouth is to be filled with
THE CHEMICAL CHARACTERS.
69
air, the passage to the lungs to be stopped by pressing
the tongue against the roof of the mouth, and this air
to be forced gently through the blowpipe by the con-
traction or compression of the cheeks and lips, the
operator breathing at the same time through his
nostrils. This, which seems difficult in the explana-
tion, is rendered very easy by practice.
The first thing to be done is to puff out the cheeks
and keep the mouth full of air, while several inspira-
tions and expirations are made through the nostrils.
After practising this simple process for a short time,
so as to be able to breathe without difficulty, the
mouthpiece of the blowpipe may be introduced gently
between the lips, and the small nozzle, being placed
just above the wick of a candle (see § B) a little within
the flame, the air may be expelled through it (by
compressing the cheeks) so as to throw the flame into
a horizontal position (see § D), as represented by fig
4, pl. I.
To perform this, the operator should sit before the
candle (the flame of which ought to be at about the
level of his mouth), and resting his elbow on the table,
he must hold the blowpipe in his right hand, as near
to the bottom or reservoir of the main pipe as con-
venient, and turn its short pipe (with the nozzle) to-
wards his left side, making it touch the flame as
directed above. The following diagram will then re-
70
CHARACTERS OF MINERALS.
present the positions of the operator, table, blowpipe,
and candle. It is advisable at first
not to attempt to direct the flame on
O
any object until able to produce a
steady and well-sustained blast, which
practice alone will enable the beginner to do.
D. Different Parts of Flame.-If we examine the
flame of a lamp or candle, we shall find it to be com-
posed of three distinct parts-namely, a dark nucleus
in the centre, formed by the unconsumed gases which
issue from the wick, and which cannot burn for want
of air; secondly, a bright luminous cone surrounding
this dark nucleus, and formed by the partial combus-
tion of the evolved gases (the carbon separating from
the carburetted hydrogen in the state of an intense
white heat); and thirdly, a thin and feebly luminous
mantle surrounding the whole flame, being scarcely
visible at the sides, but forming at the base a cup-
shaped portion of a deep blue colour. In this outer
flame the gases yet unconsumed burn freely, being
abundantly supplied with oxygen from the surround-
ing air, and it is here that the greatest degree of heat
is situated.
Now if we urge a small stream of air into the flame
of any combustible, it is immediately deflected into a
horizontal position (see fig. 4, pl. I), and oxygen,
before supplied only to the external surface, is now
THE CHEMICAL CHARACTERS.
71
thrown into its very centre, causing the complete
combustion of the gases, which burn in the form of
a small blue cone surrounded by a pointed flame
of a yellow colour. The change effected is, in the
words of BERZELIUS, "somewhat the same as if the
flame had been turned inside out."
At the point of this blue cone is concentrated all
the heat which before was spread over the external
surface; and the surrounding yellow flame prevents
the heat thus concentrated from escaping.
All bodies containing oxygen are soon deprived of
it, if held just before the point of the blue cone (but.
not within it), and this flame is therefore called the
Reducing Flame, though somewhat erroneously.
See § I, 2.)
All bodies (with a few exceptions, as platinum) are
oxygenised if held just before the point of the outer
or yellow cone, which, for that reason, is generally
termed (though also somewhat erroneously) the
Oxidating Flame. (See § I, 1.)
In simply trying whether a body be fusible or not,
it is of course to be held in the hottest part of the
whole flame, that is to say, just at the point (so as to
be touched by it) of the inner or blue cone. (See
§ I, 4.)
E. Size and Shape of the Assay.-The term "assay"
is used for brevity's sake, to express the small frag-
ment of a mineral which we submit to examination
before the blowpipe.
72
CHARACTERS OF MINERALS.
This fragment should, in general, be about as large
as the head of a common-sized pin, or a grain of
mustard seed, and occasionally even smaller. It is
almost always, by attempting to operate on fragments
of too large a bulk, that beginners fail in producing
satisfactory results.
The assay should, if possible, be of an angular or
pointed shape, and thin at the edges, as this form is
more easily acted upon by the flame than small round
or square masses. In operating upon very easily
fusible substances, however, the shape of the assay is
of little consequence. A thin pointed scale, with the
point exposed to the flame, is the best shape for trying
the fusibility of minerals of difficult fusion, or indeed
of any mineral whatsoever. (See § I, 4.)
If the assay can only be obtained in the form of
powder, it must be made to adhere by means of a
drop of water, and placed in a cavity of the charcoal,
and after a slight exposure to the flame (if it do not
fuse) the cohering mass may be held in the platinum
forceps (see § F, 2), and exposed, with its edge to the
flame, to a greater degree of heat.
F. Supports for the Assay.-These may be either
Charcoal, Platinum (in the form of forceps, foil, or
wire), or Glass (in the form of tubes, either closed at
one end, or open at both ends).
F. 1. Charcoal.-This must be well burnt, and free
from knots or cracks. The best for blowpipe pur-
poses is the "alder charcoal," which may be pur-
THE CHEMICAL CHARACTERS.
73
chased at the instrument makers in London and most
large towns, for about a shilling per pound. If living
in retired situations, the operator should take care to
provide himself with a store of this substance, which
must be kept in a tin box loosely lined with soft
Half a pound will last, with proper management, for
a long time, and in travelling, one or two good sticks,
if economised, will be sufficient for thirty or forty
assays.
paper.
The ends, or horizontal sections, of the sticks of
charcoal are to be used to support a mineral before
the blowpipe flame, and a small orifice must be cut or
scooped in them to hold the assay, and prevent it
from falling off. When the sticks of charcoal become
reduced to small pieces, they may be held in a pair of
small steel tongs, and so presented to the flame
F. 2. Platinum Forceps.-These are rather steel or
brass forceps with platinum tips. Their use is to hold
small splinters of minerals in the blowpipe flame,
which, however powerful it may be, has no effect on
platinum. This metal, however, must never be used
as a support for easily reducible substances, as most of
the ores of the common metals, nor for any substance
evolving chlorine, sulphur, &c., or it will be fused
into holes, or otherwise damaged.
All substances possessing a metallic lustre, and all
very heavy substances of a non-metallic aspect, should
therefore be first tried upon charcoal, or upon an
H
74
CHARACTERS OF MINERALS.
already damaged piece of platinum foil, which may
be kept at hand for that purpose. Very soon, how-
ever, the student will be able to determine by its
external characters, if a mineral be easily reducible or
not, except perhaps in some few peculiar cases.
Fig. 9, pl. I, represents the best kind of forceps.
A A are two thin plates of hardened steel, joined
together by a wedge-shaped piece B, of the same
metal, and each having a flat piece of platinum, P P,
riveted to one extremity. These platinum points are
kept closed by the pressure or "spring" of the steel
blades, and they are opened by pressing the finger and
thumb against the buttons of two small steel pegs, C C,
each of which passes through one blade, and is riveted
to the other. The price of these forceps is seven
shillings.
Another and cheaper kind of forceps is represented
by fig. 10. A is a flat piece of brass, having its two
ends (which are narrower than the middle) riveted
together at about half an inch from their extremities,
to which are fastened two very flat slips of platinum
with pointed tips. These are opened by pressing the
flat sides of the brass shank A, which being held in
blowpipe operations by the thin edges, no inconvenience
is felt from the heat during the strongest blast. The
price of these forceps is three shillings; they may be
purchased at Knight's, in Foster lane, and probably
at other places.
THE CHEMICAL CHARACTERS.
75
Another kind, somewhat similar to the last, has the
shank of iron wire bent into a sort of spring nippers.
The price is, I believe, about four shillings.
The great advantage which the forceps, described
above, possess over other kinds, is that they always
remain closed except when pressed upon by the finger
and thumb, owing to which any fragment may be
taken up by them in the left hand and firmly retained,
whilst the right hand is engaged with the blowpipe.
This cannot be done with the other sorts, which are,
besides, just as expensive; we therefore pass them
over without notice (and the more so, as they may be
seen at every instrument maker's), merely remarking
that the kind whose extremities are fashioned like two
earpicks, or a small cup and cover (fig. 10a), is some-
times useful for holding decrepitating minerals,* or
heating substances out of the contact of the air.
Their price varies from six to eight shillings.
F. 3. Platinum Foil.-This must be selected thin,
and cut into slips about two inches long, and half or
three-eighths of an inch broad. The mineral to be
examined must be folded in one end, or sustained
there by turning up the corners; and, as platinum
conducts heat very slowly, the other end may be held
in the fingers without inconvenience. Platinum foil
* A small glass test-tube is, however, equally serviceable for
this purpose. See further on.
76
CHARACTERS OF MINERALS.
may very well replace the "earpick" forceps de-
scribed above, for decrepitating substances, which can
be folded in it, and so prevented from dispersing;
two shillings' worth of thin foil will make several
slips of the above size. It should be mentioned, as
stated by BERZELIUS, that when we wish at the same
time to heat and oxidize any substance supported on
this material, the flame is to be directed against the
under surface of the foil, immediately below the
assay.
F. 4. Platinum Wire.-This is still more useful
than the foil, and is extensively employed for the
fusion of minerals with various fluxes or reagents.
The wire must be chosen rather thin-that is to say,
of a diameter just wide enough to withstand the force.
of the blast without bending; and it should be kept in
lengths of about three or four inches, having each
extremity bent into a small hook (see fig. 4, D). The
use of this hook is, to hold small portions of the
fluxes, &c., in the blowpipe flame, the hook or flux
being first moistened with a drop of water, or by the
mouth, so as to make the particles cohere. Being
then submitted to the flame, the flux will immediately
fuse into a small globule, which, if it appear brown or
smoked, must be kept in the blast till it become
transparent, or at least colourless, as some fluxes melt
into opaque globules. (See Fluxes and Reagents,
§ H.) Fig. 4, E, represents one extremity of a pla-
THE CHEMICAL CHARACTERS.
77
tinum wire twisted into a kind of double loop, which
is intended to hold microcosmic salt (see § H) in
the blowpipe flame, as that reagent in fusing is rarely
retained by the single hook, unless it be very narrow.
After fusing the flux or reagent, as above directed,
we add to it a few particles of the mineral which we
wish to examine, either by taking them up with the
still hot flux, or by attaching them to it, by wetting it.
when cool. We then expose the whole to the action
of the blowpipe-first before the outer, and secondly
before the inner flame-noting carefully the changes
or phenomena which take place, both whilst the bead
is hot and when cold. We refer the reader to § H
for further particulars respecting the fusion of minerals
with reagents upon this and other supports. When
we wish to detach the globules from these wires, we
must be careful in attempting to break them off, or
the hooks will come off also; it is therefore best to
dissolve them in a little water, or weak acid; and it
is, in fact, always advisable to keep the wires in a small
corked bottle or test-tube containing water.
A shilling's worth of thin platinum wire will be
sufficient to make several supports, two of which, at
least, should always be kept ready for experiments.
F. 5. Glass Tubes closed at one end.-These should
be of the hard white Bohemian, or pale-green glass,
and the operator should possess several of different.
forms. Fig. 13 represents four sorts, of which C is
H 2
78
CHARACTERS OF MINERALS.
fashioned like a common test-tube, and A has a large
bulb blown out at the closed extremity, being chiefly
used to detect the presence of water in minerals when
heated over the small spirit-lamp (fig. 3). B and D
are used for subliming arsenic, sulphur, &c., from the
minerals which contain these elements, and they are
"drawn out" or made narrow towards the closed end,
in order to prevent combustion from the access or cir-
culation of air. The most useful sizes of these tubes
are those about two and a half and three inches long,
the price of which varies from twopence to fourpence
each. For further particulars, see § I, 3.
F. 6. Glass Tubes open at both ends.-These must
be made of the same kind of glass as the above; flint
glass containing lead (which may be known by its
turning black before the point of the inner flame, the
lead being reduced) is utterly useless for blowpipe
purposes. The length of these tubes should be about
four inches, and their internal diameter one-eighth of
an inch. The price of tubing of this size of Bohemian
glass is about twopence farthing per foot. This sup-
port is used for roasting minerals or subliming certain
of their constituents, and the assay is to be placed
within the tube, at about an inch from one extremity,
and the flame directed upon the outside of the tube
immediately beneath it. The position of the tube
must be generally inclined, but it may be either
raised to a vertical position, or lowered to a horizontal
THE CHEMICAL CHARACTERS.
79
one, according as we wish to increase or diminish the
current of air through it. See also § I, 3.
G. Other necessary or useful Instruments. — A
small agate mortar and pestle. The bottom of the
mortar should be somewhat transparent, for the reason
shown at § I, 2. Its external diameter need not ex-
ceed an inch and a half, nor its height half an inch.
The price of a mortar of this size is about six shillings,
but cheaper, though far less useful kinds, may be had
of Berlin porcelain for a shilling, or of thick glass for
sixpence each. A mortar of hard steel, composed of
two pieces, with a tightly-fitting pestle, is also useful
for crushing hard substances; but it is rather expen-
sive, and the hammer and anvil will answer the same
purpose.
A small microscope or pocket-lens, for examining
the assays after exposure to the blowpipe, the colours
which they impart to the reagents, the results of sub-
limation, &c. It may be had of all prices, but in a
neat tortoise-shell case to protect the glass, for half-a-
crown or three shillings. The price of the small
powerful Codington lens varies from seven shillings to
a guinea.
A knife with a straight blade, having a slightly
rounded point. It is used to mix the fluxes with the
powdered assay, to knead them in the palm of the left
hand, to try the hardness or streak of any mineral, &c.
Knives made for mineralogical purposes have at the
80
CHARACTERS OF MINERALS.
bottom of the handle a strong piece of polished
steel, which serves, in a degree, the purpose of a
hammer.
A small hammer of hardened steel. One face must
be square, with sharp edges, for trying the malleability
of substances, and the opposite end should be bevelled
off like a chisel, to detach small fragments of minerals,
&c. The price of a hammer of this kind is eighteen-
pence.
A small block of hardened steel, about two inches
square and three-quarters of an inch thick, polished
upon one or more of its faces. It should have a cover
of wash-leather to protect it from rust. To test the
malleability of the reduced globules of metal, as ob-
tained by the blowpipe, or of small fragments of mi-
nerals, we fold them in a piece of thin paper, and
placing them on a polished face of this little anvil,
strike them one or two smart blows with the flat face
of the hammer, after which, unfolding the paper
(which prevents the substance from dispersing, and
the corner of which may be held during the operation
by the fore-finger of the left hand), we find either a
flat shining spangle, or some powder. In the former
case, the globule would be malleable; in the latter,
brittle. If the bottom of the anvil be unpolished,
mineral specimens may be broken into shape upon it.
The price of an anvil of this description is about three
shillings.
THE CHEMICAL CHARACTERS.
81
Two or three fine hard files, for trying the degrees
of hardness of minerals, cutting glass tube, &c.
A magnetic needle and centre. An electrometer.
A small spirit-lamp. These have been already de-
scribed. A platinum spatula is also very useful, but
it is expensive; and the blade of the knife, just de-
scribed, supplies well enough its place in blowpipe
operations.
A washing-bottle for reducing experiments. (See
§ I, 2.) This is a common flask or bottle, having a
small glass tube with a very fine external orifice
passed through its tightly-fitting cork. If, after half
filling the bottle with water, and inserting the cork,
we blow through this fine orifice for a few seconds,
and then invert the bottle, a minute stream of water
will be expelled through it, as shown at fig. 12, owing
to the dilatation of the compressed air within. The
price of a bottle of this kind is one shilling. In tra-
velling, the small tube only need be carried about, as
it can be adapted to almost any bottle. The tube itself
may also be made from a piece of common glass
tubing, by drawing out one extremity in the flame of
the spirit lamp.
A small spoon (bowl about half an inch in diameter),
made of very thin iron or steel, with a cover, and
wooden handle. Price about half-a-crown.
One or two small capsules of platinum, also of
Berlin porcelain, for heating acid solutions over the
82
CHARACTERS OF MINERALS.
spirit lamp, and also for holding the small mineral
fragments to be examined, &c.
A few bent iron wires, to support the above, or
better still, a small jointed triangle of brass, which
may be made to fit over the stem of the blowpipe lamp,
described in § B.
A pair of small steel tongs for trimming the lamp,
and other purposes. (See § H. 1, note.) The price
of these tongs is one shilling.
A few test tubes of hard German glass, and a tube-
holder, made of japanned tinned iron plate, and so
constructed as to shut flat when not in use. This is
done by attaching together the four pieces of which
it is composed, by means of hinged joints. The price
of a test-tube holder of this description is eighteen-
pence. Tinned iron plate, japanned, is less costly
than brass, and infinitely preferable.
A tray of sheet iron, not tinned, in which the lamp
or candle is to be placed during operations, and which
serves to retain the assay if it should fall, or be blown
off its support. A common earthenware dish may
serve, however, as a substitute for this tray.
The following articles will also be found useful, and
should therefore be included in the complete minera-
logical chest.
A pair of strong cutting pliers, for detaching small
portions from a specimen without injuring it. These
may be had combined with a pair of common pliers.
THE CHEMICAL CHARACTERS.
83
A small vice. A
good pieces of cork.
pair of scissors. Two or three
A set of cork borers ("Griffin's
pattern"). A thin saw blade, for sawing the char-
coal into shape. A small funnel of Berlin porcelain,
or of glass. Some iron and brass wire. Three or
four small cloths, about a foot square, made of thin
material (such as diaper), for wiping the blowpipe,
agate mortar, and other articles. Some wash-leather,
&c. A few other instruments of minor importance
will probably occur to the operator in the course of
practice; and should he extend his researches beyond
the bounds of mineralogy into those of its parent che-
mistry, he will of course require a much more complex
and expensive set of apparatus.
H. Blowpipe Reagents, and method of using them.--
The term "reagent" is applied to any substance
which, on being added in particular manners to other
substances, produces in them peculiar changes or
phenomena, whereby their nature is made known to
us. Thus, if a little borax or microcosmic salt be
added to a few minute particles of a mineral contain-
ing cobalt, and the whole be then fused together, the
melted bead will become of a fine blue colour. Borax
and microcosmic salt (especially the former) are
therefore excellent reagents or tests, when used in this
manner, for detecting the presence of cobalt in mine-
ral substances.
The principal blowpipe reagents (some of which are
often termed fluxes) are the following:-
>
84
CHARACTERS OF MINERALS.
H. 1. Carbonate of Soda.-For brevity's sake, in
mineralogical works, this flux or reagent is simply
termed "soda." It must (as well as every other re-
agent) be perfectly pure; and before using it, the
operator should test if it contain any sulphuric acid or
not, as sulphate of lime is often mixed with the car-
bonate of soda of commerce. This may be done by
simply fusing a little of it before the point of the blue
or inner blowpipe flame,* either on charcoal or the
platinum wire, when, if it contain sulphuric acid, the
melted bead will become (instead of being colourless)
of a yellowish, reddish, or brown colour, according to
the quantity of the intermixed sulphate.
In using this reagent on charcoal, it will be found
to sink into the support; but on continuing the blast,
it will rise again to the surface, and act (if able to do
so) on the mineral attempted to be fused with it. The
method of mixing this flux, as well as the two follow-
ing, with any substance, prior to exposure to the blow-
pipe flame, is described in the accompanying directions.
First, moisten the point of the knife-blade or spatula,
and dip it into the pounded flux. Secondly, wet the
palm of the left hand with the tongue, and knead upon
* The reader will please to observe that the following abbre-
viations will often be made use of in the subsequent pages of
this work:-O. F. signifies the point of the outer or yellow flame;
I. F. signifies the point of the inner or blue flame; C. signifies
charcoal; P. F. platinum foil; P. W. platinum wire; S. carbo-
nate of soda; B. borax; M. S. microcosmic salt.
THE CHEMICAL CHARACTERS.
85
the spot, the particles adhering to the blade, so as to
make them cohere. Thirdly, place the paste thus
formed on its support, and fuse it into a globule.
Fourthly, reduce to powder the mineral fragment to
be examined, and make a small quantity adhere to this
globule by wetting it; the whole may be then fused
together. Or, the powdered mineral may be added to
the flux before fusion, being kneaded with it in the
palm of the left hand, as described in the second stage
of the proceeding, and this method is perhaps prefer-
able in some cases.
The beginner is here cautioned, in all experiments,
to add the mineral particles very sparingly to the
fluxes, otherwise these will not act properly on the
assay, or will be so deeply coloured as to appear black
and opaque.*
Soda is chiefly used in reducing experiments, for an
account of which see § I, 2, and also for detecting
sulphurets and sulphates, oxide of manganese, and
silica in its simple state-for an explanation of which,
the reader is referred to the APPENDIX at the end of
the volume. It is likewise used for the fusion of some
substances, in order to render them soluble in water,
in which state their natures may be ascertained by
various liquid tests.
* In that case, more of the flux must be added, or the colour
may be sometimes distinguished by pinching the bead flat
(whilst still hot) between a pair of small steel tongs.
I
86
CHARACTERS OF MINERALS.
H. 2. Borate of Soda, or Borax.-This reagent,
when not calcined, intumesces or curls up very much
when presented to the blowpipe flame; but on con-
tinuing the blast, it melts into a transparent and
colourless globule. It is principally used to detect
the nature of substances by the colours which, during
fusion, they impart to it-for a description of which
consult the APPENDIX at the end of the volume. Some
bodies also have the property of fusing with borax
into a clear glass before the I. F., but which becomes
opaque or clouded when acted upon by the point of
the O. F., or by either flame in an intermittent man-
ner. (See § 1, 6.) Platinum wire is the best support
for this reagent.
H. 3. Phosphate of Soda and Ammonia, or Mi-
crocosmic Salt.-On exposure to the blowpipe, this
reagent boils and intumesces, giving out ammonia,
and tinging the flame slightly green. The moment
the intumescence subsides, it runs into such liquid
fusion that, if supported on platinum wire, it generally
falls from it unless the loop be very narrow, or twisted,
as described at § F, 4, and represented at fig. 4, E,
pl. I. The bead should be perfectly transparent,
otherwise the reagent is impure. Microcosmic salt,
like borax, is also used to detect substances by the
colours which they impart to it when fused together,
or by their relative degrees of fusibility in it-as, for
instance, "silica," which remains totally insoluble.
THE CHEMICAL CHARACTERS.
87
For further particulars, see the APPENDIX at the end
of the volume.
H. 4. Bisulphate of Potash.-This reagent is
chiefly used to discriminate Nitrates, Fluorides, &c.,
as will be explained in the APPENDIX. It should be
melted and reduced to powder, and kept in a small
glass bottle for use. A sufficient quantity, however,
for two or three hundred assays may be purchased,
ready prepared, for sixpence.
H. 5. Nitrate of Cobalt.-This must be a pure
concentrated solution, dissolved in water. It may.be
kept in a small bottle, with a well-fitting cork, which
should be sealing-waxed on the outside. Into this
cork it is convenient to insert a piece of platinum
wire (reaching to the bottom of the bottle, and beaten
flat at that extremity), which serves to take up a drop
or two of the solution, and to which the cork forms a
handle in experimenting. This very useful reagent is
employed to detect the presence of alumina, magnesia,
and oxide of zinc, imparting to them respectively a
blue, pale reddish, and green colour-if they be
moistened with a drop of it, and heated to redness on
charcoal; a little previous manipulation is, however,
necessary. In order to absorb the solution properly,
the mineral to be tested must first be reduced to
powder, and ground up with a little water in the agate
mortar, so as to form a kind of paste. This paste is
then to be placed on the charcoal and
heated, when
88
CHARACTERS OF MINERALS.
the water will be absorbed, and a drop or two of the
reagent being added to the powdered mass, the whole
is to be again heated gradually up to a strong red
heat, and then left to get cool, as until quite cold the
colour does not become properly developed. It should
also be examined by daylight, as the colours appear
almost alike, or muddy, by the light of a candle.
Note. In testing minerals by this reagent, it is necessary to
observe: first, that the red tint imparted to magnesia is exceed-
ingly feeble; secondly, that silica (heated with it, as described
above) generally takes a weak tinge of blue, though very dif-
ferent to the deep blue colour imparted to alumina; thirdly,
that lime and the alkalies also become blue, but not unless they
be fused with the solution; and fourthly, that nitre, if present
in any mineral, or if added to it, will render it blue when heated
with this reagent, even though it contain no alumina. These
circumstances must, therefore, be retained in the memory.
H. 6. Saltpetre (Nitre).—This reagent is used to
promote oxidation, in fusing substances with borax,
&c. (so as to develop the colour imparted to the flux),
by plunging into the bead, whilst still hot, the end of a
long thin crystal, which is to be held in the steel
tongs. The fused globule immediately bubbles up
and foams, and the imparted colour becomes apparent
as the bead gets cold, though often only on its edges, if
the colouring oxide contained in the assay be in minute
quantity. Nitre is also used to detect organic bodies,
ignited with which it produces a sudden deflagration.
H. 7. Tin.-This is to be used in the state of thin
THE CHEMICAL CHARACTERS.
89
resist
foil closely rolled up, so as to form small pointed.
cones. It is employed to promote reduction in sub-
stances which, when fused with the fluxes,
strongly the action of the reducing flame by thrusting
the end of the small roll into the fused bead whilst
still hot. Part of the tin fuses, and is retained in the
bead, which is then again to be exposed before the
point of the blue flame, but only for an instant or two,
as otherwise the tin will render the globule opaque,
and destroy the effects intended to be produced.
H. 8. Silica. This reagent may be obtained by
pounding rock-crystal, so as to reduce it to a fine
powder. It is used in this state when fused with car-
bonate of soda, to discriminate sulphurets and sul-
phates, which impart to the fused bead (when melted
with it) a dark brown or red colour, particularly as
it cools. For other methods of detecting these com-
pounds, see the APPENDIX at the end of the volume.
H. 9. Oxide of Copper.-This reagent is used to
detect the presence of chlorine. It must be first fused
with microcosmic salt on the platinum wire, and a
small particle of the mineral containing chlorine is
then to be added, when the flame will instantly assume
a powerful and beautiful blue colour. This process
may, however, be simplified by making use of a thin
copper wire, upon which to fuse the microcosmic salt,
instead of a platinum wire, in which case the oxide of
The copper wire
copper is of course not wanted.
I 2
90
CHARACTERS OF MINERALS.
must be bent into a double loop, as shown at E, fig. 4,
and the end must always be cut off and thrown away,
after each experiment.
H. 10. Bone-ashes and Refined Lead.-See "Cupel-
lation," I. 7.
H. 11. Test Papers.-The following are required:
Litmus paper, which reddens on the application of
acids; turmeric paper, which turns brown on the ap-
plication of alkalies;* Brazil-wood paper, which be-
comes bleached by sulphureous vapours, and rendered
yellow by those of fluorine; and lead paper (paper
dipped in a solution of lead, and dried for use), which
becomes black when acted upon by sulphuretted hy-
drogen, and serves for the detection of sulphurets and
sulphates. See the APPENDIX. A common glazed
visiting card will, however, answer the same purpose.
A new or bright silver coin is also useful in de-
tecting the two latter compounds. (See the AP-
PENDIX.)
H. 12. Fluor-Spar and dried Gypsum are usually
included amongst blowpipe reagents, being used
mutually to detect each other, as they fuse together
(in certain proportions) into a clear glass, which be-
comes opaque on cooling. Fluor-spar is also used in
conjunction with bisulphate of potash (in the ratio of
In testing the reactions of water driven off from minerals
by heat (see § I, 3), ammoniacal water will give this effect.
THE CHEMICAL CHARACTERS.
91
one part of the former to four and a half parts of the
latter) to detect boracic acid, as when fused with any
mineral containing it, the flame takes a momentary
tinge of dark green. Methods, however, as simple,
and more effective, to discriminate this acid, will be
given in the APPENDIX at the end of the volume.
Hydrochloric acid and Sulphuric acid (previously
described, see Action of Acids) are also occasionally
required in blowpipe experiments. (See § I, 5.)
I. Simple Blonpipe Operations.
I. 1. Oxidation.-To oxidize any substance, we
have merely to hold it for a sufficient time before the
point of the yellow or outer blowpipe flame, and as
far from it as will serve to keep the assay at a dull
red heat. This process is so simple that it requires
no further explanation in the present place. (See
§ D, and also I, 3.)
I. 2. Reduction.-There are some ores of metals
which may be converted or reduced into a reguline
state by simply holding them for a shorter or longer
time before the point of the inner or blue flame, and
entirely within the yellow flame, when the sulphur,
oxygen, &c., with which they may have been com-
bined, is driven off or consumed by the flame, and a
"button" of metal more or less pure remains upon
the charcoal. This substance should always be used
as a support in the reduction of metallic ores, as it
has a powerful deoxidizing effect, and is not of course.
92
CHARACTERS OF MINERALS.
acted upon by the metal; in some peculiar cases,
however, glass tubes may be used, when we wish at
the same time to reduce the metal, and retain the sub-
limed matter for examination. (See I, 3.)
The method of reducing difficultly-reducible com-
pounds, or those containing but a small proportion of
metal, is the following:-
The assay is to be crushed to powder, and mixed
with carbonate of soda. Secondly, the mixture is to
be placed on charcoal, and fused before the I. F., till
the soda be absorbed by the charcoal. Thirdly, more
of the flux is to be added, and the whole again ex-
posed to a well-sustained blast (always before the
I. F., see § D), until flux and assay disappear within
the pores of the support, more soda being added if the
second supply do not effect this. Fourthly, the ignited
charcoal is to be quenched with a drop or two of
water, and the space around the cavity where the
assay rested is to be cut out, and carefully placed in
the small agate mortar (§ G), so as not to lose any
of the particles. Lastly, this is to be ground to a fine
powder by means of the pestle, and the charcoal is to
be washed out gradually by projecting a minute
stream of water upon it from the washing bottle de-
scribed in § G. This process requires great care and
some skill (only to be acquired by practice) to prevent
the small metallic particles from being carried off with
the charcoal powder; but if it be properly performed,
THE CHEMICAL CHARACTERS.
93
66
these will be found, after several "grindings" and
washings," at the bottom of the mortar, in the
form of small flattened grains or spangles if malleable
and fusible, or in that of a dark metallic powder if
brittle or infusible. On holding the bottom of the
mortar up to the light, these must appear quite opaque;
and this is mentioned, as occasionally in mortars that
are much used, small cavities get worked in them,
which, filled with air, form bubbles, that appear by
reflected light like metallic spangles; but being trans-
parent, their true nature is at once perceived when
examined, as directed, by refracted light.
The sides and bottom of the mortar are always (if
any reducible metal be present in the assay) marked
with metallic traces, and these must be removed after
each experiment by means of a piece of pumice or a
little wet bone-ash.
If, instead of carbonate of soda alone, we employ a
mixture of that flux and cyanide of potassium, the
reduction will be more speedily effected. The two
fluxes may be mixed in about equal proportions, or
with rather more of the latter; but cyanide of potas-
sium is too rapidly absorbed by the charcoal to be
used alone.
I. 3. Roasting and Sublimation.-These operations
are similar in their actions and effects, with this excep-
tion, namely that in the former case we do not seek
to retain the volatile matters driven off, whilst in sub-
94
CHARACTERS OF MINERALS.
limation our attention is particularly directed to the
examination of their properties. Before attempting
to reduce any mineral, we must first expose it to as
strong a heat as it will bear without fusing, and this
must be particularly attended to, as if it fuse, the ope-
ration is useless. This process is best conducted on
charcoal, and the assay must be exposed to the O. F.,
or, if it contain arsenic, to the O. F. and I. F. alter-
nately.
The surface of the charcoal, after and during the
roasting of most volatile substances, becomes covered
with a crust of oxidized metal, which sublimes before
the I. F. A white crust indicates antimony, arsenic,
tellurium (sometimes yellowish), tin (very slight),
or zinc (yellowish whilst hot). A yellow sublimate
indicates bismuth, lead, or cadmium (orange yellow).
The ash of the charcoal may sometimes be mistaken
by beginners for a sublimate, but it may be distin-
guished from such by remaining unaltered before the
inner flame.
In volatilizing on charcoal, most combinations of
sulphur give out a sulphureous odour; those of arsenic
an alliaceous or garlic-like odour; those of selenium,
an odour resembling that of decayed horse-radish;
and those of antimony and tellurium slightly pungent
odours.
In subliming the volatile constituents of minerals,
so as to be able to examine the results of sublimation,
THE CHEMICAL CHARACTERS.
95
we make use of small glass tubes, closed at one end,
or open at both ends, as explained at § F, 5 and 6. If
we wish to try if a mineral contain water, we employ
a small flask or tube with its closed end blown out
into a bulb, into which we place a few fragments of
the specimen to be examined, and heat it gently over
the flame of the small spirit-lamp, when the water (if
any be present) will rise and condense upon the upper
part of the tube. This water may be tested for acid or
alkaline reactions, with small slips of test-paper, as
described at § H, 10; if it have no effect upon them,
it is said to be "neutral." Tubes of this kind, but
with a very small bulb, or "drawn out to a fine
point," and of narrow diameter, are also used for sub-
liming arsenic, &c. ; but if sublimed per se, the open
tube is preferable and less expensive, as a fresh one is
required for every operation. In experimenting,
however, upon very minute quantities, these closed
tubes must be used, and the assay reduced to powder
is mixed with certain reagents or fluxes, and placed in
the narrow part or small bulb, and this being heated
either by the spirit-lamp or blowpipe, the volatilized
and reduced metal rises, and forms a crust on the
cool sides of the tube. The reagents chiefly used for
these purposes are: carbonate of soda (previously
ignited or dried), formate of soda, and cyanide of
potassium, or a mixture of one part of cyanide of potas-
96
CHARACTERS OF MINERALS.
sium and three parts of carbonate of potash.* The
pulverized assay should be not only mixed, but also
well covered with, the flux, and the tube must be held
horizontally, and heated for some distance around the
assay, as well as immediately beneath it. It is almost
needless to observe, that all tubes (open or closed)
used in these experiments should be perfectly dry, to
ensure which they ought to be gently heated before
being used.
In employing open tubes for sublimation, we are to
follow the directions given at § F, 6—namely, to
place the assay at a short distance from one extremity,
and to expose it to the point of the inner blowpipe
flame, when its volatile constituents (if it contain any)
will rise and condense on the cool sides of the tube
above it. For this purpose the tube should be gene-
rally held in an inclined position, and in operating the
two chief effects to be looked for are: the odours
evolved during the experiment, and the resulting sub-
limate.
These effects, as exhibited by the different consti-
tuents of minerals, will be fully described in the Ap-
PENDIX at the end of the volume.
I. 4. Trial of Fusion, &c.-Characters developed
during the trial.-Results of the trial.-In order to try
* FRESENIUS.
*
THE CHEMICAL CHARACTERS.
97
if a body be fusible per se or not, we first place it on a
piece of charcoal, and expose it to the inner flame, as
if it be reducible, &c. (see § F, 2), it will injure a
platinum support. This preliminary proceeding may,
however, be generally dispensed with, as the beginner
will soon be able to judge, from its external characters,
if a mineral be reducible or not, and the following
remarks may guide him in so judging. Reducible
minerals, of a non-metallic aspect, are generally very
heavy, or have a coloured streak, and their degrees
of hardness are rarely above 3.5 or 4.0. Minerals of a
true metallic aspect should always be tried on charcoal,
as there are very few which do not injure platinum.
Being thus certain, or nearly so, as to the relative
reducibility of the mineral under examination, we
take a small splinter of it (see § E), supposing it to be
not reducible, and expose it to a good and well-con-
tinued blast, in the platinum forceps (§ F, 2), holding
it at the point of the blue flame.
In this position some minerals remain totally un-
altered, as kyanite; others either decrepitate (fly to
pieces, see § F, 2), and remain unaltered, or rather
unfused, as diaspore; or otherwise curl up exceedingly
(intumesce), and afterwards resist fusion, as epidote.
A few infusible minerals also change colour, and
become attractable by the magnet, as siderose.
The fusible minerals either decrepitate before fusion,
as barytine, or intumesce before fusion, as stilbite, or
K
98
CHARACTERS OF MINERALS.
***
otherwise fuse with more or less bubbling, as datho-
lite; or with effervescence and sputtering, as olivenite
(this mineral destroys platinum); or else fuse quietly,
as analcime.
The different degrees of fusibility are also charac-
teristic, thus: cryolite fuses very easily; wernerite
easily; feldspar rather difficultly; and emerald very
difficultly. The colours which some minerals impart
to the flame are likewise to be particularly noticed.
(See § I, 5.)
The results of fusion may be either-
A glass, colourless or coloured, clear and trans-
parent (ex. harmotome), or blebby, full of air-bubbles
(ex. stilbite).
An enamel or opaque glass, coloured or colourless
(ex. barytine). A very blebby glass resembles an
enamel.
A frit, or semi-fused mass.
A slag.
A scoria, or small light mass, resembling a cinder
(ex. melantherite).
66
A metallic bead or button," which may be either
malleable or brittle, and which must be tried, there-
fore, on the anvil, as described at § G. This bead, as
well as the other results of fusion, may also or may
*This character is often confounded with intumescence; but
intumescence takes place previous to fusion-bubbling during
fusion.
THE CHEMICAL CHARACTERS.
99
not attract the magnet; and this must be attended to
in the examination.
Note.-In inspecting the results of fusion, sublimation, &c.,
the magnifying glass should always be made use of.
I. 5. Production of Coloured Flames.-The tints
which some substances impart to the blowpipe flame
form an interesting and easily-developed character,
and one of no mean importance in the discrimination
of minerals and their constituent parts.
In trying if a mineral possess this character, a wax
candle, with rather a slight wick, must be selected, so
as to give (when acted upon by the blowpipe) a small,
clear, thin, and sharply-pointed flame, of a pure blue
colour, just within the point of which the fragment
under examination is to be held. The following is a
tabular view of the principal elements and their com-
binations which impart a colour to flame. See also
the APPENDIX at the end of the volume.
Impart a YELLOW tint to the flame.
Soda: if held at a short distance from the flame's point, the
colour will be more strongly developed.
Impart a GREEN tint to the flame.
Copper: carbonate of copper, iodide of copper, &c.
Tellurium.
Ammonia: a dark tint of little duration.
Boracic acid: the borates should be moistened with sulphuric
acid.
Phosphoric acid: a pale tint. The phosphates should be pre-
viously moistened with sulphuric acid.
100
CHARACTERS OF MINERALS.
Sulphuret of molybdenum.
Baryta a pale apple-green colour.
Zinc: a very pale tint.
Antimony: a bluish-green tint.
Impart a BLUE colour to the flame.
Chloride of copper.
Selenium.
Sulphur.
Bromide of copper: green at the edges.
Lead: a very pale tint.
Arsenic a pale greenish-blue tint.
Impart a RED or CRIMSON colour to the flame.
Strontia: a deep crimson tint, which is the more strongly de-
veloped in the salts of strontia by moistening them with hydro-
chloric acid.*
Lithia a purplish-red colour, which is rendered more appa-
rent in minerals containing lithia, if they be fused with bisul-
phate of potash.
Lime a yellowish-red colour, rendered more apparent by
moistening the assay with hydrochloric acid.
Potassa a violet-red tint, rendered imperceptible by the pre-
sence of soda.
I. 6. Flaming.-This operation consists in expos-
ing any substance, after fusion with borax on the
platinum wire, to the action of an intermittent flame,
which may be done by simply keeping the flame
* Sulphate of baryta and sulphate of strontia greatly resemble
each other, but the former imparts a pale green tint to the
flame, the latter a reddish tint, or a deep crimson colour, if
moistened with hydrochloric acid.
THE CHEMICAL CHARACTERS.
101
steady, and moving the globule in and out of it a few
times. The object of this process is to see if the
globule retain its transparency, or become clouded or
opaque. The latter will invariably be the case if it
contain any of the following substances-that is to
say, if they be in sufficient quantity, and uncombined
with silica or alumina :
The alkalies, lime, magnesia, strontia, baryta,
glucina, yttria, zirconia, oxide of cadmium, ox. of
zinc, ox. of columbium, ox. of titanium, and ox. of
cerium.
I. 7. Cupellation.-This is the process of separating
the "noble metals," silver and gold, from other sub-
stances by heat, and obtaining them in a state of
purity. It is not often required in blowpipe experi-
ments, but is, nevertheless, a very interesting opera-
tion, and essential to be known. The following is
the method of proceeding, as described by BER-
ZELIUS:-
"A small quantity of bone-ashes (in powder) is to
be taken on the point of a knife moistened with the
tongue, and kneaded in the palm of the left hand
with a very little soda into a thick paste. A hole is
then made in a piece of charcoal, and filled with the
paste, and its surface smoothed by pressure with the
* Page 64 of Mr CHILDREN'S translation.
K 2
102
CHARACTERS OF MINERALS.
agate pestle. It is then to be gently heated by the
blowpipe till perfectly dry. (The soda only assists
the cohesion, and may be omitted.) The assay, pre-
viously fused with pure lead, is placed in the middle
of this little cupel, and the whole heated by the ex-
terior flame. When the operation is finished, the
precious metals are left on the surface of the cupel.
This experiment is so delicate, that grains of silver
visible to the naked eye, and indeed such as may be
collected by the forceps and extended under the
hammer, may in this way be extracted from the lead
met with in commerce."
*
K. General method of examining a mineral sub-
stance.—The first thing to be done is to note down
carefully its principal external characters. Aspect,
hardness, streak, and colour, can always be examined
in the merest fragment; specific gravity, if the spe-
eimen be not too small, or otherwise consisting of
disseminated particles; and form, if it be unbroken or
perfect. The properties of taste, magnetism, &c., as
described in the first part of this work, are also, of
course, to be attended to.
This examination being finished, and the results
written down in a small book which should be kept
* The lead being converted into the state of an oxide,
and absorbed by the bone-ash support, owing to its porous
nature.--E. C.
THE CHEMICAL CHARACTERS.
103
for the purpose, the mineral is to be tested with a
little dilute and concentrated nitric or hydrochloric
acid, in order to see if it be soluble, if it form a jelly,
or effervesce, &c.; and this is to be done both in a
small test-tube, without the application of heat, and
in a small porcelain or platinum capsule, supported on
a bent wire over the flame of a spirit-lamp.
Lastly, the specimen is to be examined by heat and
the blowpipe, in the following order :-
1. It is to be heated in a test-tube or matrass over
the flame of a spirit-lamp, to see if it decrepitate,
phosphoresce, give off water, yield a sublimate, &c.
2. It is to be roasted before the blowpipe in a small
tube open at both ends, to see if it be volatilizable
wholly or in part, with or without odour; if it form a
sublimate, &c.
3. It is to be exposed to the blowpipe on charcoal,
-first, before the O. F., and afterwards before the
I. F.-to see if it give off any fumes or odour, if it
form a crust on the support, if it fuse, if it be re-
ducible, &c.
4. It is to be tried in the platinum forceps, to see in
it colour the flame, if it intumesce, if it fuse (quietly
or with bubbling), if it yield a glass or enamel, &c.
5. It is to be melted (if possible) either on charcoal
or the platinum wire, with borax, to see if it reduce, if
it fuse quietly or not, if it yield a coloured glass, or
one that becomes opaque by flaming, &c.
104
CHARACTERS OF MINERALS.
6. It is to be tried in the same manner with micro-
cosmic salt.
7. With soda.
8. With any other reagents that may be thought
necessary, from the characters developed during the
preceding operations.
APPENDIX.
A BRIEF COMPENDIUM OF THE ELEMENTS OF
QUALITATIVE MINERAL ANALYSIS.
I. Preliminary Remarks.
*
THERE are in nature a certain number of substances,
which individually have never been decomposed or
subdivided into other substances, and which are,
therefore, termed "simple or elementary bodies."
Of two or more of these elementary bodies, all other
substances are composed, in certain definite propor-
tions.
It is the object of qualitative analysis to detect the
presence of as many of these bodies as may be com-
bined in any compound.
The elementary bodies hitherto discovered are the
following:-
Platinum.
Palladium.
Rhodium.
Osmium.
* In this brief outline, only the most simple discriminating
characters, such as can be developed by the blowpipe and its
usual apparatus, will be given.
106
CHARACTERS OF MINERALS.
Iridium.
Gold.
Silver.
Mercury.
Bismuth.
Lead.
Copper.
Iron.
Antimony.
Arsenic.
Tellurium.
Selenium.
Sulphur.
Carbon.
Hydrogen.
Nitrogen.
Fluorine.
Chlorine.
Iodine.
Bromine.
Oxygen.
Titanium.
Columbium (or Tantalum).
Tungstenum.
Molybdenum.
Chromium.
Vanadium.
Aluminium.
Silicium.
Boron.
Phosphorus.
Nickel.
Cobalt.
Manganese.
Tin.
Zinc.
APPENDIX.
107
Cadmium.
Cerium.
Uranium.
Thorinium.
Zirconium.
Yttrium.
Magnesium.
Calcium.
Strontium.
Barium.
Sodium.
Potassium.
Lithium.
A few of these elementary bodies are found in
nature in a simple or uncombined state. These arc
mineralogically termed native substances.
All combinations consist of mineralizers and bases.
By "mineralizers we understand such elements as
have the power of mixing with other elements so as
to change their appearance, and modify their proper-
ties; and by "bases," we understand the elements so
combined with.
A compound may contain one element, or a com-
bination of two elements, as a mineralizer, and one or
several bases.
Compounds containing a combination of two ele-
ments as a mineralizer are chemically termed "salts."
All the inorganic substances, or minerals, which
occur in nature may therefore be classed in two
groups, namely—simple substances and compound
108
CHARACTERS OF MINERALS.
substances; and the latter may be subdivided into
other
groups, according to their different mineralizers.
The following arrangement will, therefore, repre-
sent the divisions, to some one of which every mineral
substance is referrible :-
NATIVE SUBSTANCES.
ANTIMONIURETS: mineralized by antimony.
ARSENIURETS: m. by arsenic.
TELLURETS: m. by tellurium.
SELENIURETS: m. by selenium.
SULPHURETS: m. by sulphur.
ANTIMONIO-SULPHURETS:* m. by antimony and sulphur com-
bined.
ARSENIO-SULPHURETS:* m. by arsenic and sulphur combined.
CARBURETS: m. by carbon.
OXIDES: m. by oxygen.
TITANIATES: m. by oxygen and titanium combined.
COLUMBATES: m. by oxygen and columbium combined.
TUNGSTATES: m. by oxygen and tungstenum combined.
MOLYBDATES: m. by oxygen and molybdenum combined.
CHROMATES: m. by oxygen and chromium combined.
VANADIATES: m. by oxygen and vanadium combined.
ALUMINATES: m. by oxygen and aluminium combined.
SILICATES: m. by oxygen and silicium combined.
BORATES: m. by oxygen and boron combined.
PHOSPHATES: M. by oxygen and phosphorus combined.
ARSENIATES: m. by oxygen and arsenic combined.
SULPHATES: m. by oxygen and sulphur combined.
CARBONATES: m. by oxygen and carbon combined.
NITRATES: m. by oxygen and nitrogen combined.
* These are often termed sulphur-salts.
† These combinations (terminating in ate) are termed
oxygen-salts.
APPENDIX.
109
FLUORIDES: m. by fluorine.
CHLORIDES: m. by chlorine.
IODIDES: m. by iodine.
BROMIDES: m. by bromine.
Note.—The mineralizing combinations of oxygen with other
elements are termed "acids," as titanic acid, molybdic acid,
silicic acid, sulphuric acid, &c.
II. Discrimination of the Class or Order to which a
Mineral may belong, and detection of its component
elements.
If a mineral be a native substance, it must be one
of the following:—
Platinum: L. metallic; C. white; infusible; in-
soluble in nitric acid.
Palladium: L. metallic; C. white, or pale-steel
grey; infusible; soluble in heated nitric acid, solu-
tion of a red colour.
Osmium, iridium: these occur in nature only in
conjunction, with a small portion also of rhodium.
The osmium may perhaps act the part of a mineralizer.
Osm-iridium is brittle; L. metallic; infusible; sp.
gr. above 18.0; insoluble, even in aqua-regia.
Gold: C. yellow; ductile; fusible.
Silver: C. white; ductile; fusible.
Mercury: C. white; volatilizable; yielding a sub-
limate in the form of small metallic globules, and if
L
110
CHARACTERS OF MINERALS.
mixed with silver (in which case it may perhaps act
the part of a mineralizer), a bead of that metal will
remain behind.
Bismuth L. metallic; C. reddish-white, not
malleable; fusible and volatilizable, leaving a yellow
crust (of oxide of bismuth) on the charcoal.
Lead: C. grey; malleable; fusible and volatiliza-
ble, leaving a yellow crust (of oxide of lead) on the
charcoal.
Copper: C. copper-red; malleable; fusible; giv-
ing with borax a fine green glass, which becomes blue
when cold, before the O. F., and a red opaque glass
before the I. F.; soluble in nitric acid, and in am-
monia; solution of a blue colour.
Iron : C. grey; infusible; attractable by the
magnet; giving with borax before the I. F. a dirty
green glass.
Antimony: C. tin-white; brittle; easily fusible;
volatilizable; leaving a white crust on the charcoal,
and yielding in the glass tube a pulverulent uncrys-
talline sublimate.
Arsenic: C. grey, tarnishing black; brittle; fusi-
ble and volatilizable, with a strong odour of garlic,
leaving a white crust on the charcoal, and yielding
in the tube a dark metallic sublimate, or a white
crystalline one, in the form of minute (regular) octa-
hedrons.
Tellurium: C. white; brittle; easily fusible, and
APPENDIX.
111
volatilizable; leaving on the charcoal a white or
yellowish-white crust, and yielding in the tube a sub-
limate capable of fusion into white limpid drops.
:
Sulphur aspect non-metallic; very soft; inflam-
mable; burning with a blue flame, and strong odour
of brimstone; volatilizable in the open tube, bleach-
ing a slip of moistened Brazil-wood paper placed at
its upper part.
Carbon the Diamond: aspect non-metallic;
harder than all other bodies. A very minute splinter
may be volatilized on charcoal in a long-sustained
blast, but it is a difficult operation for beginners; the
surface is, however, soon deprived of its polish.
;
Note.-Copper imparts a deep green colour to the flame
antimony, tellurium, and arsenic a light green tint. Lead and
bismuth deposit a yellow crust on the charcoal; lead is malleable,
bismuth brittle. The tube sublimates of mercury, antimony,
arsenic, and tellurium are very characteristic, as is also the
garlic-like odour of arsenic in volatilizing. Copper, gold, and
silver are fusible, and the first imparts a colour to borax. Iron,
platinum, palladium, and osm-iridium are infusible; the first
colours borax, and is magnetic. Palladium is soluble in nitric
acid, and platinum in aqua-regia. Sulphur is inflammable, burn-
ing with a blue flame and strong odour of brimstone, and the
diamond is the hardest substance in nature.
There is no fixed character applicable to all the
native substances, consequently we must refer to the
characters peculiar to each. If the mineral under
examination do not accord with any of the above, it
will be referrible to one of the following divisions:-
112
CHARACTERS OF MINERALS.
Antimoniurets: aspect metallic; volatilizing like
native antimony (see above), but leaving a residue*
behind.
Arseniurets: aspect metallic; volatilizing like
native arsenic (see above), but leaving a residue
behind.
Tellurets: aspect metallic; volatilizing like native
tellurium (see above), but leaving a residue behind.
Seleniurets: aspect metallic; volatilizing (in part)
with a strong odour of decayed horse-radish, and
yielding in the open tube a red sublimate.
Sulphurets: aspect metallic and non-metallic;
partly or wholly volatilizable in the open tube; bleach-
ing a slip of moistened Brazil-wood paper, placed at
its upper part, and giving out generally a sulphureous
odour; forming also, by fusion with carbonate of
soda on charcoal, a brown or reddish compound,
which, moistened with water (or better still, with
acidulated water), emits sulphuretted hydrogen,
known by its nauseous taste and odour; and if this
be done on a bright silver coin or on a slip of “lead
paper," a black stain (of sulphuret of silver or lead)
will be formed.
Antimonio-sulphurets: giving the above reactions,
combined with those of antimony. The simple sul-
* This residue is of course a base; its characters must, there-
fore, be compared with those of the "bases" further on.
APPENDIX.
113
phuret of antimony is entirely volatilizable; the anti-
monio-sulphurets leave a residue.
Arsenio-sulphurets: giving the reactions of arsenic
and sulphur. The simple sulphurets of arsenic are
entirely volatilizable; the arsenio-sulphurets leave a
residue. They form also in the open tube, at a low
degree of heat, a reddish sublimate of sulphuret of
arsenic; others yield the metallic sublimate of arsenic,
or the crystalline deposit of arsenious acid.
Carburets: the only mineral carburet which occurs
in a solid state is the carburet of iron, and that sub-
stance is generally considered to be a mechanical
mixture of carbon and iron. The following cha-
racters distinguish it from all other minerals:-aspect
metallic; H=1.0-2.0; infusible; not affected by the
fluxes.
Fluorides: aspect not metallic; exposed to the
blowpipe flame (in a tube closed at one end) with bi-
sulphate of potash, with sulphuric acid, or with
microcosmic salt (previously fused), they disengage
hydro-fluoric acid, which corrodes the glass, and
changes the colour of a moistened slip of Brazil-
wood paper, placed at its mouth, to yellow. If the
tube be breathed into, the corroded surface will be
rendered more perceptible.
Chlorides: aspect not metallic; imparting to the
flame, when fused with microcosmic salt on a fine
copper wire, a beautiful and powerful blue colour.
L 2
114
CHARACTERS OF MINERALS.
Iodides: imparting to the flame a fine emerald-
green colour, when fused on a copper wire, with
microcosmic salt.
:
Bromides: imparting to the flame a blue colour,
mixed with green, when treated in the above manner.
Oxides it is impossible to detect the presence of
oxygen in minerals by any simple assay; it must
therefore be done by comparing the characters of
the mineral under examination with those of all the
foregoing and following divisions, when, if they do
not agree, we may be satisfied that it is a simple oxide
or acid. If it agree, however, with some one of the
following divisions, all of which are double com-
pounds of oxygen, or oxygen salts (see the first
section of this APPENDIX), it may still be a simple
acid; as, for instance, the general character of the
titaniates is applicable to titanic acid, a simple com-
bination of oxygen, the bases of the double combina-
tions or salts not being in all cases determinable by
simple blowpipe experiments.
Titaniates: forming with borax, before the I. F.,
a dark amethyst-coloured glass, which may be ren-
dered of a lighter colour (or colourless), and opaque
by flaming. If the titaniates contain a large portion
of iron, they impart to microcosmic salt a red colour,
but the glass assumes an amethystine tint on the
addition of tin. Pure titanic acid is infusible, and
not reducible. With borax, it gives the above result,
APPENDIX.
115
and with soda on the platinum wire it forms a yellow
glass, which on cooling becomes colourless, and emits
numerous sparks. On charcoal this glass crystallizes
with the evolution of great heat.
Columbates: giving, by fusion with carbonate of
soda, a compound soluble in water, the solution pre-
cipitating, on the addition of nitric acid, a white
powder, which yields with borax a colourless glass,
that may be rendered opaque by flaming. Pure
columbic acid is infusible, and not reducible.
Tungstates: forming, with borax, a yellowish glass
(or a red one if the assay be in excess) before the I. F.,
and imparting to microcosmic salt, before the same
flame, a blue colour, unless iron be present, in which
case the glass is of a red tint; but this is dispelled by
tin, and the glass turns green or blue. With soda on
charcoal, by the reducing process, p. 92, the tungstic
acid is converted into a grey metallic powder (tung-
stenum).
Molybdates: forming, with microcosmic salt before
the I. F., a green glass. With borax, the glass is of
a yellow tint, or colourless. With soda on charcoal,
by the reducing process, p. 92, the molybdic acid is
converted into a grey metallic powder (molybdenum).
Chromates: forming with borax, microcosmic salt,
* Only one molybdate (the molybdate of ox. of lead, Prac-
tical Mineralogy,' p. 41) has hitherto been found in nature.
116
CHARACTERS OF MINERALS.
and soda, green glasses. With the latter reagent the
glass is opaque. Pure oxide of chrome is infusible,
and not reducible.
Vanadiates: forming with borax and microcosmic
salt, before the I. F., green glasses. Fused alone on
platinum foil, a red matter is produced.
#
Aluminates: forming, with carbonate of soda, a
compound, generally infusible, and more or less
soluble in acids; the solution yielding a gelatinous
precipitate on the addition of ammonia, which becomes
of a fine blue colour when ignited with nitrate of
cobalt. Pure alumina behaves in the same manner,
and forms, with borax and microcosmic salt, colour-
less glasses, which cannot be made opaque by
flaming.
Silicates: forming (though with difficulty), by
fusion with carbonate of soda, a matter soluble in
water; the solution yielding a white precipitate by
evaporation, which fuses, with soda, into a clear
glass, and does not colour the other fluxes.
Several silicates are partly soluble in acids, forming
a transparent gelatinous mass, caused by the separa-
tion of the silica. Pure silica, or silicic acid, fuses
with carbonate of soda (with effervescence) into a
clear, colourless glass, but it remains undissolved
* A vanadiate of ox. of lead ('Practical Mineralogy,' p. 42)
has hitherto only been met with in nature.
APPENDIX.
117
in microcosmic salt, forming a "skeleton" in the
centre of the bead.
Borates: partly soluble in nitric acid, leaving a
residue, which imparts to alcohol the property of
burning with a green flame. The borates also colour
the flame green, when moistened with sulphuric acid
and exposed to the blowpipe.
Phosphates: colouring the blowpipe flame pale
green when moistened with sulphuric acid. Also
forming, by fusion with carbonate of soda, a sub-
stance soluble in water-the solution yielding a yellow
precipitate, with nitrate of silver.
Arseniates: partly volatilizable before the blowpipe
on charcoal, with a strong odour of garlic. No
metallic lustre.
Sulphates: no metallic lustre; forming, with car-
bonate of soda on charcoal, a brown or reddish com-
pound, which, moistened with water (or acidulated
water), emits sulphuretted hydrogen, known by its
disagreeable taste and odour, which resemble those of
putrid eggs; and if this be done on a bright silver
coin, or on a slip of "lead paper," a dark stain (of
sulphuret of silver or of lead) will be produced.
Carbonates: soluble, with more or less efferves-
cence, in hot or cold acids, disengaging carbonic acid
gas. No metallic lustre; H. under 4.5; streak, not
red.
118
CHARACTERS OF MINERALS.
Nitrates soluble in water; deflagrating more or
less when mixed with charcoal (or any organic sub-
stance) and ignited, and giving out the red fumes of
nitrous acid when heated, in a small tube closed at
one end, with bisulphate of potash.
We have now to consider the bases which may be
contained in the above compounds. These, for con-
venience, may be arranged in two groups-the first.
containing the non-oxidized, and the second the
oxidized bases.
Non-oxidized Bases.
These occur in a native state, or mineralized by
arsenic, antimony, tellurium, selenium, sulphur,
carbon, fluorine, chlorine, iodine, bromine, or
oxygen.
Silver.
Mercury.
Bismuth.
Lead.
Copper.
Iron.
See the "Native Substances" above.
Antimony.
Arsenic.
APPENDIX.
119
Nickel: metallic aspect ;* magnetic; not volatiliza-
ble; soluble in nitric acid; forming a green solu-
tion, which changes to a violet colour on the addition
of ammonia.
Cobalt metallic aspect;* magnetic; not volatiliza-
ble; soluble in nitric acid, solution pale red;
forming, by fusion with borax, a deep blue glass.
Manganese:+ aspect metallic; infusible, and not
volatilizable; forming, with carbonate of soda, on the
platinum foil or wire, before the blowpipe, a green
enamel, which becomes blue when cold.
Tin: aspect metallic; malleable; easily fusible;
and in a slight degree volatilizable, the areola being
white and inflammable. The small malleable globule
on charcoal might be mistaken for silver or lead, but
the former is not at all volatilizable, and the latter
deposits a yellow crust on the support.
Zinc: never obtained in the metallic state before
the blowpipe; forms, when strongly heated on char-
coal, a sublimate of oxide of zinc-yellowish whilst
hot, white when cold.
*In blowpipe experiments, after driving off the sulphur,
arsenic, or other mineralizers from the assay, the base remain-
ing has generally a dark earthy aspect; but if it really possess
a metallic lustre, the same may be rendered evident by rubbing
it on the file or in the agate mortar.
There is but one mineral (with the exception of the oxides
of this metal) which has for its base manganese in a simple
state; it is the alabandine or sulphuret of manganese.
120
CHARACTERS OF MINERALS.
Cadmium: never obtained in the metallic state
before the blowpipe; forms, on charcoal, a dark
orange-yellow sublimate.
Molybdenum: yielding on charcoal, before the
blowpipe, with soda, dark metallic grains; detonating
with saltpetre.
Cerium,*
Yttrium,
Magnesium,
Calcium,
Sodium,
Potassium,
Aluminium,
as mineralized by fluorine, or chlo-
rine, cannot in blowpipe experi-
ments be distinguished from their
oxides, which see.
The only remaining bases are those solely mineralized
by oxygen, and they cannot, in these experiments, be
obtained in a free state. These are: titanium, mo-
lybdenum, tungstenum, chromium, aluminium, and
silicium, all of which have been described above
Oxidized Bases.
Oxide of Bismuth: easily reducible before the
blowpipe to the metallic state, when it behaves of
course like pure bismuth. (See the preceding group.)
Oxide of Lead: easily reducible to the metallic state,
when it behaves of course like pure lead. With borax,*
* In these experiments the fluxes are supposed to be supported
on the platinum wire, unless the contrary be mentioned.
APPENDIX.
121
before the O. F., it forms a yellowish glass, which
becomes colourless when cold.
Oxide of Copper: easily reducible; forming with
borax, before the O. F., a green glass, which turns
blue upon cooling, and becomes, before the I. F., dark
red and opaque.
Oxide of Iron: reducible (into a grey metallic
powder), with soda on charcoal in a good blast;
blackening and becoming magnetic per se; forming,
with borax and microcosmic salt, before the O. F.,
red glasses, which become almost colourless when
cold; before the I. F., these glasses take an impure.
green colour.
Oxide of Nickel: alone, unalterable before the
blowpipe, but reducible with soda on charcoal; form-
ing with borax, before the O. F., a red or yellowish
glass, which becomes nearly colourless on cooling, but
if saltpetre be added, it takes a blue tinge. Before
the I. F. the glass turns grey, owing to the presence
of reduced metal. With microcosmic salt, before both
flames, the glass is pale yellow or colourless, when
cold.
Oxide of Cobalt: unalterable alone, reducible
with soda on charcoal;* forming, with borax and
microcosmic salt, beautiful dark blue glasses. A
* The reduced particles of nickel and cobalt, it will be re-
membered, are, like those of iron, attractable by the magnet.
M
122
CHARACTERS OF MINERALS.
very minute quantity of the oxide only must be used,
otherwise the glasses will appear black and opaque.
Oxide of Manganese: infusible per se, but turns
brown; not reducible with soda on charcoal; form-
ing with soda, on the platinum foil or wire, a green
glass, which on cooling becomes of a greenish-blue
colour, and opaque. This is the principal blowpipe
test for manganese. With borax and microcosmic
salt, it forms amethyst-coloured glasses before the
O. F., which, exposed before the inner flame, become
colourless. The borax glass if saturated, however,
will recover its violet tint unless it be suddenly cooled
by being plunged into cold water, or blown upon.
Oxide of Tin: difficultly reducible per se, but
very easily reducible with soda on charcoal, forming
a metallic button. To the fluxes on the platinum
wire it imparts no colour; the borax and micro-
cosmic salt glasses are not rendered opaque by
flaming.
Oxide of Zinc: infusible; becoming yellowish
whilst hot; volatilizable slowly before the I. F.,
leaving a white crust on the charcoal, and shining
with bright greenish-white light. It volatilizes more
readily when mixed with carbonate of soda; forming,
with borax and microcosmic salt, colourless glasses,
which are rendered opaque by flaming. With nitrate
of cobalt, it takes a green colour (see p. 87).
Oxide of Cadmium: reactions similar to those of
APPENDIX.
123
•
oxide of zinc, with the exception of depositing an
orange-yellow crust on the charcoal.
Oxide of Cerium: infusible, and not reducible;
forming with borax and microcosmic salt, before the
O. F., red or orange-yellow glasses, which become
colourless (or nearly so) on cooling, and also when
exposed before the I. F. The borax glass may be
rendered opaque by flaming.
Oxide of Uranium: per se blackens, but does not
fuse. With borax and microcosmic salt it forms,
before the O. F., yellow glasses, which become green-
ish when cold. Before the I. F. the borax glass is of
a dirty green colour, and may be rendered almost
black by flaming, if the oxide be in excess; the
microcosmic salt glass takes a fine green tint. With
soda on charcoal no reduction is effected.
Oxide of Thorinium: infusible per se; not reduci-
ble with soda; forming, with borax and microcosmic
salt, colourless glasses, which become opaque when
flamed.
Oxide of Zirconium (Zirconia);
Oxide of Glucinium (Glucina);
Oxide of Yttrium (Yttria);
Oxide of Magnesium (Magnesia);
Oxide of Calcium (Lime);
Oxide of Strontium (Strontia);
Oxide of Barium (Baryta);
Oxide of Sodium (Soda);
124
CHARACTERS OF MINERALS.
Oxide of Potassium (Potassa);
Oxide of Lithium (Lithia);
infusible; not reducible; forming, with borax and
microcosmic salt, colourless glasses, which turn
opaque when flamed.
Note.-Zirconia and lime emit a powerful light when exposed
to the blowpipe flame; the other oxides do the same, though in
a far less intense degree. Magnesia, treated with nitrate of
cobalt (see p. 87), takes a pale flesh-red colour. Strontia (par-
ticularly if moistened with a little hydrochloric acid) colours
the blowpipe flame bright red; baryta, pale green; soda, yellow;
potassa, violet; lithia, and also lime (if moistened with an acid),
purplish-red (see p. 99).
Oxide of Titanium. (See Titanic acid, p. 114).
Oxide of Aluminium. (See Alumina, p. 116).
Retrospect.
1. VOLATILIZABLE BASES.
Mercury (p. 109).
Bismuth (p. 110).
Lead (p. 110).
Zinc (p. 119).
Cadmium (p. 120).
Tin, in part (p. 119).
Antimony (p. 110).
Arsenic (p. 110).
Molybdenum, in part (p. 120).
2. BASES YIELDING per se, A REGULINE METALLIC GLOBULE.
Silver (p. 109).
Mercury (p. 109).
APPENDIX.
125
Bismuth (p. 110).
Lead (p. 110); ox. of lead (p. 120).
Copper (p. 110); ox. of copper (121).
Nickel (p. 119).
Cobalt (p. 119).
Antimony (p. 110).
Arsenic (p. 110).
Tin (p. 119); ox. of tin (p. 122).
3. BASES NOT REDUCIBLE per se, BUT YIELDING, WITH SODA
ON CHARCOAL,* REGULINE METALLIC GRAINS.†
Oxide of Iron (p. 121).
Oxide of Cobalt (p. 121).
Oxide of Nickel (p. 121).
Molybdenum (p. 120).
4. BASES WHICH IMPART A COLOUR TO BORAX OR
MICROCOSMIC SALT.
Copper (p. 110); ox. of copper (p. 121).
Iron (p. 110); ox. of iron (p. 121).
Nickel (p. 119); ox. of nickel (p. 121).
Cobalt (p. 119); ox. of cobalt (p. 121).
Manganese (p. 119); ox. of Manganese (p. 122).
Molybdenum (p. 120).
Ox. of Uranium (p. 123).
Ox. of Titanium (p. 124).
Ox. of Lead (p. 120) colourless when cold.
Ox. of Cerium (p. 123)
* See the "Reducing Process," p. 92.
The mineralizing acids reducible by this means are the
tungstic and molybdic acids.
M 2
126
CHARACTERS OF MINERALS.
:
5. BASES WHICH FORM, WITH BORAX, GLASSES THAT MAY BE
RENDERED OPAQUE BY FLAMING.
Note.
Ox. of Cerium (p. 123).
Ox. of Titanium (p. 124).
Ox. of Zinc (p. 122).
Ox. of Cadmium (p. 122).
Zirconia (p. 123).
Yttria (p. 123).
Glucina (p. 123).
Lime (p. 123).
Magnesia (p. 123).
Strontia (p. 123).
Baryta (p. 123).
The mineralizing acids, which form similar glasses
with borax, are the tungstic, titanic, and columbic acids.
THE END,
POSTSCRIPT.
DURING the printing of this work, I have added a
third plate, representing a modification of the old
instrument for taking specific gravities, which pos-
sesses the advantage over the areometer, described at
page 10, of requiring for its use merely a glassful of
water. This advantage, in travelling especially, is
not to be despised, as it is often very difficult to find
a vessel of convenient form sufficiently deep to con-
tain the floating balance, and still more difficult to
procure the necessary quantity of distilled, or even of
rain water, with which to fill it. The instrument
represented at plate 3 has likewise the advantage of
being more readily managed, the weights in using
the areometer being liable, unless carefully handled,
to be precipitated to the bottom of the vessel; and
the specific gravities of larger fragments may be
taken with it, so as to avoid the necessity, in common
cases, of breaking up choice specimens. As this
instrument takes to pieces, its portability is equal to
that of the areometer, and it is besides of so simple a
construction, that it may be procured from any scale-
maker's.
128
CHARACTERS OF MINERALS.
Description of Instrument for taking Specific
Gravities. (Plate 3.)
A is an "upright" of brass, screwing into the lid
of the box, B. For the sake of portability, this
upright may be in two pieces screwing together at
the centre.
C is a brass hook or pin (fitting into the upright),
from which the balance D, of hard steel, is suspended.
D' D" are thin brass rods, hooking on to the beam
of the balance.
E is the cup for the weights.
F is a piece of metal beneath, to poise the weight
of the apparatus on the other side.
G and H are the cups for the mineral whose sp. gr.
we wish to ascertain. It is of course first to be
weighed in G, and afterwards in H, as in the areo-
meter (page 11).
I is a glass nearly full of distilled or rain water, in
which the cup H is to be immersed during operations.
The instrument is to be so constructed as that one
side shall exactly counterpoise the other, when the
cup H, and about two inches of the rod D" (which at
that part should be as thin as possible), are under
water.
If a the weight of the mineral when in the cup
G, and b = its weight when in the cup H, then :
a
ab
sp. gr. sought.
POSTSCRIPT.
129
In conclusion, I beg to state, that the idea of
having the two cups on one rod is not my own. It
is either the invention of M. Brard, of Paris, or of
M. C. Paul, of Geneva; their instruments I have
never seen, but they are constructed, I believe, with
a sliding weight, similar to the steel-yard.
NOTE TO THE READER.
It was my intention to have prefixed to this little
treatise "A New Artificial Arrangement for the
Discrimination of Minerals," differing from that
given in the second part of Practical Mineralogy,'
to which it would form a kind of check or proof;
but this the busy nature of my avocation compels me
for awhile to relinquish. It will however, I trust,
be shortly completed, and will be published so as to
bind up, if required, with the present volume.
E. C.
Manningham, near Bradford, Yorkshire,
March 23, 1844.
LONDON:
PRINTED BY REYNELL AND WEIGHT, PULTENEY STREET, HAYMARKET.
1
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;
CHAPMAN'S
MINERAL CHARACTERS.
ERRATUM.
THE Balance in Plate 3, has been incorrectly represented. The cups as
there shown, attached to a single rod, would fall out of the line of suspension,
-they should therefore have been drawn as represented below:-


D
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Fig. 6.
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Fig. 11.
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13
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​Plate 2.








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E
F
D
A
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Plate 3.


BOUND BY
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LONDON
1
UNIVERSITY OF MICHIGAN
3 9015 06437 8758

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​hirt.
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