4 QUARTZ. 
wood, it is called woodstone. J.ydian stone, some- 
times called flinty slate, differs from flint chiefly in 
having a darker colour, less translucency, and a frac- 
ture somewhat slaty; when black, it is often called 
bassanite. Floatstone consists of a delicate tissue of 
minute crystals, visible only under a powerful magni- 
fier. Owing to the cavities it contains, it sometimes 
will float on water. Fibrous quartz consists of those 
varieties which are in distinct, parallel concretions. 
Radiating quartz is like fibrous quartz, except that 
the fibres diverge from a common centre, and resem- 
ble the radii of a circle, instead of being parallel. 
Chalcedony includes those varieties of radiating 
quartz, where the thickness of the individuals be- 
comes so much diminished as to render them nearly 
or altogether impalpable; its masses generally offer a 
mammillary or stalactitical surface, and the lustre on 
freshly-broken surfaces is feeble. Carnelian differs 
from chalcedony merely in having a blood-red colour. 
Chrysoprase also resembles chalcedony in composi- 
tion, excepting that the individuals of which it is 
made up, appear to be grains instead of fibres; its 
colour is apple-green, from the oxide of nickel. Agate 
implies the occurrence of two or more of the above 
varieties, existing together in intimate union; or it 
may be applied to a single variety, provided it offers 
different colours im the same specimens. 
Those substances which have formerly been in- 
cluded under quartz, and which are mixtures only of 
this mineral with other species, are the following: 
1. cat’s eye; 2. avanturine ; 3. prase; 4. plasma; 5. 
heliotrope; 6. tron flint; 7. Compostella hyacinth ; 
8. jasper (red, brown, striped and porcelain) ; 9. jas- 
per-agate; 10. Mocha stone; 11. Venus-hair agate. 
Cat’s eye consists of transparent quartz traversed by 
exceeding'y delicate parallel fibres of asbestus; when 
eut en cabuchon, it exhibits, as its position is altered 
to the eye, a peculiar play of light upon its surface, 
resembling the changeability of light seen in the eye 
ofacat. Avanturine is guartz penetrated by small 
golden-coloured spangles of mica. Prase is quartz 
penetrated by green fibres of hornblende, which are 
often so small as te escape detection by the naked 
eye, and their presence is only discoverable from the 
green colour they impart. Plasma is a variety of 
chalcedony, coloured leek-green by some substance 
not yet examined. Heliotrope is likewise a variety 
of chalcedony, but coloured by green earth, and oc- 
casionally dotted with minute portions of red jasper. 
Tron flint consists of quartz, intermingled throughout 
with oxide ef iron. ‘The Compostella hyacinth is a 
red variety of iron flint, in regular six-sided prisms, 
with pyramidal extremities, which occurs imbedded } 
in gypsum. Jasper differs from the two last varieties 
in being massive, and in containing variable propor- 
tions of clay. Red and brown jasper simply allude 
to the colour of the compound. Striped jasper ap- 
pears to contain a larger portion of clay, and is distin- 
guished on account of its striped delineations. Por- 
celain jasper is regarded as siliceous slate altered by 
heat, and is found in the vicinity of coal-mines. Those 
varieties which are found in rounded masses, and 
which, from the concentric layers of which they con- 
sist, appear to have been formed in open spaces, are 
called Egyptian jasper. Jasper agate consists of those 
varieties of jasper in which several colours are so ar- 
ranged as to produce an agreeable effect. Mocha 
stone consists of agate, containing appearances of 
vegetable filaments, which have been occasioned 
through the infiltration of iron and manganese through 
its crevices. Wenus-hair agate consists of quartz 
traversed by delicate hair-shaped crystals of any kind. 
The most transparent varieties of quartz are pure 
silex, which, according to Berzelius, contains 49°70 
silicon and 50°30 oxygen. Hornstone, flint and chal- 
cedony agree with it in composition. Several varie- 
ties contain small qnantities of alumine, lime, oxide 
| being composed of silex. 
-silver. 
QUASSIA. 
of iron, &e. 
nickel, 
Quartz is infusible before the blow-pipe, and shows 
itself to be pure silex. It is dissolved by seda easily, 
and with effervescence. Two pieces rubbed toge- 
ther emit an empyreumatic odour, and a phosphores- 
cent light. Crystals of quartz may be obtained from 
a solution of silica in fluoric acid, or in potash diluted 
with water. The fiuid from which crystals of this 
species are formed, in geodes and other natural cavi- 
ties of rocks, has been observed to be chiefly water. 
With respect to the distribution of quartz, and 
which we have remarked above to be the most abun- 
dant mineral known, it may be said that common 
quartz enters into the regular mixture of various 
rocks, of granite, gneiss, mica slate, topaz rock, &e. 
In others, it occurs in single crystals and in grains, 
Chrysoprase contains 0.01 oxide of 
as, for instance, in porphyry, and is frequently met 
with in the vesicular cavities of amygdaloidal rocks. 
In these last situations, in particular, are found the 
finest varieties of chalcedony, carnelian, of jasper and 
agate. Hornstene forms globules and irregular veins 
in compact limestone; and flint occurs in a similar 
manner, but disposed through vast beds of chalk. 
Quartz, also, occurs in rocks, of whieh it does not 
form a regular ingredient ; sometimes in masses that 
are open in their interior, and lined with crystals of 
enormous size. It also exists in beds by itself, as in 
quartz-rock, and some varieties of sandstone. Striped 
jasper and flinty slate form, also, particular beds. The 
varieties prase and chalcedony, as well as amethyst, 
are often found in beds of iron ore. River sand, and 
that of extensive plains, where it is sometimes so fine 
as to drift before the wind, are formed chiefly of 
quartz. Common quartz, and several other varie- 
ties, are spread all over the earth, but certain varie- 
ties are confined to a few localities. The finest and 
largest rock crystals are found in the Alps of Salz- 
burg, the Tyrol, Switzerland, Dauphiny, Piedmont, 
}and Savoy; also in the isle of Madagascar, Ceylon, 
and Brazil. 
Several varieties of quartz are of important use 
in the arts and manufactures, and have long been 
employed for purposes of decoration and utility 
by mankind. The most important applications of | 
this species to useful purposes, depend upon its 
Quartz enters into the 
composition of glass, both white and coloured. 
It is added to the mass of porcelain, in the state 
of an impalpable powder, and forms part of the 
paste, also, in other kinds of pottery. It is used 
as a flux in the melting of several kinds of ores, 
particularly those of copper, and in other metal- 
lurgical processes. The use of flint in gun-locks 
is well known. lydian stone is employed for 
trying the composition of mixtures of gold and 
Sandstone yields various applications for 
architectural and other purposes, as the con- 
struction of melting- furnaces, mill-stones, é&c. 
A variety of sandstone from Villa Rica, in Brazil, 
which is flexible, deserves to be spoken of in this 
place. Its flexibility is probably owing to scales 
of mica disseminated through its mass. Sand, 
with slaked lime, forms mortar. It is also used, 
in some countries, for the improvement of roads. 
See the articles Stnica and Sanp. 
QUASSIA. A small genus of ligneous, ever- 
green, tropical plants, of the simaruba order. 
The bitter species, Y. amara, was introduced to 
Britain from Guiana in the latter part of last 
