202 
MINERALOGY. 
2. Friable Minerals. 
The externa! characters drawn from mine- 
rals of this class are derived, first, from the 
external shape, which may be massive, dis- 
seminated, thinly coating, spumous, or den- 
driiic: secondly, from the lustre, regarded 
under its intensity, whether glimmering or 
dull, and its sort, whether common glimmer- 
ing or met Hie glimmering : thirdly, from the 
aspect of the particles, as being dusty or 
scaly : fourthly, from soiling or colouring, as 
strongly or lightly : and lastly, from the fri- 
ability, which may be loose or cohering. 
* 3. Fluid Minerals. 
Of external characters drawn from fluid 
minerals, there are only two kinds, which in- 
clude three varieties : t . The lustre, which is 
either metallic, as in mercury, or resinous, as 
in rock oil. 2. The transparency, which is 
transparent, as in naphtha; turbid, as in mine- 
ral oil ; or opaque, as in mercury. 3. The 
fluidity, which may be fluid, as in mercury, 
or viscid, as in mountain tar. 
External Characters from the Smell. 
These may be spontaneously emitted and 
described, as bituminous, faintly sulphureous, 
or faintly bitter; or they may be produced by 
breathing on, and yield a clay-like smell ; or 
they may be excited by friction, and smell 
urinous, sulphureous, garlick-like, or empy- 
reumatic. 
External Character from the Taste. 
This character prevails chiefly in the sa- 
line class, and it contains the following va- 
rieties: a sweetish taste, sweetish astringent, 
styptic, saltly bitter, saltly cooling, alkaline, 
or urinous. 
Having now given a synoptical view of the 
external characters of minerals, we shall pro- 
ceed to their classification, and in this we 
shall chiefly follow the names and arrange- 
ment of professor Jameson. 
CLASS I. 
EARTHY FOSSILS. 
First Genus. Diamond. 
Diamond. 
This precious stone has great variety of 
shades, exhibiting a beautiful play of co- 
lours. It occurs in indeterminately angular 
and completely spherical grains, which pre- 
sent planes of chrystallization, or are actually 
cnrystallized. Its fundamental chrystal is the 
, octaedron, which passes into various forms. 
It is hard in the highest degree, brittle, not 
very difficultly frangible, and has a specific 
gravity of 3.600. 
The diamond has, by modern experiments, 
been proved t© be nearly pure carbon, and 
begins to burn at 14° or 15° of Wedge- 
wood.- See Plate I. Mineralogy, figs. 1. and 2. 
Second Genus. Zircon. 
First Species. Zircon. 
The prevailing colour is grey, but it occurs 
likewise green, blue, red, yellow, and brown, 
with various intermediate tints. 
It is found most commonly in roundish 
angular pieces, with rounded angles and 
edges. When chrystallized, the figure is ge- 
nerally a rectangular four-sided prism, some- 
what flatly acuminated by four planes, set on 
lateral planes ; but of this figure there are se- 
veral varieties. The chrystals are almost al- 
ways very small, have a smooth surface, 
bordering on strongly splendent. Internally, 
the lustre is strongly splendent, passing into 
adamantine. Fig. 3. 
Zircon is hard in a very high degree, brit- 
tle, frangible without great difficulty. Spe- 
cific gravity 4.700. It forms a colourless 
transparent mass with borax, but is infusible 
by the blowpipe without addition. 
Found in the island of Ceylon, where it 
was first discovered, and lately in Norway, 
imbedded in a rock composed of hornblende 
and felspar. 
Frequently cut as a precious stone, and 
used as an inferior kind of diamond, of which 
it was once considered as a variety. Its play 
of colours very considerable. 
Second Species. Hyacinth. 
The chief colour is red, passing to reddish- 
brown, and to orange-yellow. The figure a 
rectangular four-sided prism, flatly acumi- 
nated by four planes, which are set in the la- 
teral edges. Of this figure, however, seve- 
ral varieties occur. 
The chrystals are generally small, and al- 
ways imbedded. The lateral planes smooth, 
and externally shining. Internally it is 
splendent and glassy, inclining somewhat to 
resinous. Fig. 4. 
The hyacinth is transparent, very hard, 
frangible without particular difficulty,' feels a 
little greasy when cut, and has a specific 
gravity of about 4.000. 
Is fusible with borax. Exposed to the 
blowpipe it loses its colour, but not its 
transparency. 
Occurs in rocks of the newest fioetz trap 
formation, and sometimes in sand. Is a na- 
tive of Ceylon, the country of gems ; of 
Spain, of Portugal, France, Italy, Saxony, 
and probably Scotland. 
It takes a fine polish, and when the colours 
are good, it is highly valued. A third spe- 
cies, called cinnamon stone, has lately been 
discovered at Columbo, in Ceylon. 
Third Genus. Flint. 
First Species. Chrysoberyl. 
The prevailing or general colour is aspara- 
gus-green, passing into a variety of allied 
shades. It exhibits a milk-white light ; oc- 
curs in roundish and angular grains, which 
sometimes approach in shape to the cube. 
It is seldom chrystallized ; but when in this 
state, it commonly presents a longish six- 
sided table, having truncated lateral edges, 
and longitudinally streaked lateral planes. 
The chrystals are small, externally shining, 
and internally splendent. Fig. 3. 
It is hard, brittle, not very easily frangible, 
with a specific gravity of 3.600. Without 
addition, it is infusible. 
The chrysober) 1 is found in Brazil, and in 
the sand of Ceylon. It is sometimes set in 
rings with a yellow foil, but is rarely in the 
possession of our jewellers. 
Second Species. Chrysolite. 
The chief colour is pistachio-green, of all 
degrees of intensity. It occurs in original 
angular sharp-edged pieces, with a rough, 
scaly, splintery surface,, and when chrystal- 
lized, exhibits a broad rectangular four-sided 
prism, with its lateral edges sometimes trun- 
cated, sometimes bevilled, and acuminated 
by six planes. Fig. 6. 
The external surface of the chrystals is 
splendent, internally splendent, and vitreous. 
Third Species. Olivine. 
The colour is generally asparagus-green, 
of various degrees of intensity. It is lound 
imbedded also in roundish pieces and grains ; 
and when chrystallized, which is rare, in rec- 
tangular four-sided prisms. 
Internally, it is shining, varying between 
glistening and splendent. It is semitrans- 
parent, very easy frangible ; in a low degree 
hard, and not particularly heavy. It is 
nearly infusible without addition. Occurs 
imbedded in basalt ; is frequently found in 
Bohemia, and also in Hungary, Austria, 
France, England, Ireland, Scotland, Sweden, 
Iceland, and Norway. Pieces as large as ; 
a man’s head have been found in some parts 1 
of Germany. 
Fourth Species. Augiie. 
The general colour is blackish green. It 
occurs chiefly in indeterminate angular 
pieces and roundish grains. Occasionally it 
is chrystallized, and presents broad rectangu- 
lar six-sided prisms. The chrystals are 
mostly small. Internally the lustre is shin- i 
ing, approaching sometimes to splendent. * j 
The augite is only translucent, and but 
faintly transparent. It is hard, not very \ 
easily frangible, and not particularly heavy. ; 
It is found in basalt, either singly or ac- ; 
companied with olivine, in Bohemia, Hun- 
gary ; at Arthur’s-seat, near Edinburgh ; in 
some of the Hebrides, and in Norway. : 
From olivine it is distinguished by its darker 
colours, the form of its chrystallization, and 
its greater hardness. 
Fifth Species. Vcsuviane. 
Its principal colour is dark olive-green, 
passing into other allied shades. It occurs 
massive, and often chrystallized in rectangu- ' 
laf four-sided prisms. The chrystals are 
mostly short, and placed on one another. 
Externally their surface alternates between 
glistening and splendent. Internally they 
are glistening, with a lustre between vitreous 
and resinous. 
The vesuviane is translucent, hard in a mo- 
derate degree, and approaching to heavy. ; 
Before the blowpipe it melts without a’d-j 
dition. 
It is found among the exuviae of Vesuvius, 
from whence it derives its name, in -Siberia 
ami Kamtschatka. At Naples, it is cut into 
ring-stones, and sold under various names. 
Sixth Species. Leuzite. 
The colours are yellowish and greyish- 
white. It occurs mostly in original round 
and angular grains. When chrystallized, it 
exhibits acute- double eight-sided pyramids.! 
| Internally it is shining, and; approaching to 
glistening, with a vitreous lustre, inclining 
j somewhat to resinous. 
The leuzite is translucent and semitrans- 
parent. It is hard in a low degree, brittle, 
easily frangible, and not very heavy. It is 
infusible without addition. With borax, it 
! forms a brownish transparent glass, 
j It is found in rocks of the newest fbetz. 
1 8 . 
