15 
Figs. 8-19.— The Garnet. 
The Garnets belong to the most abundant, various, 
and finest of precious stones, although they certainly are 
but little valued on account of their frequency and cheap¬ 
ness. 
The primary form is a rhombic dodecahedron (Fig. 8), 
which very frequently occurs without any further combi¬ 
nations. Besides this truncation of all the edges (Figs. 9 
and 18), double truncation of the same (Fig. 11), and the 
trapezohedron (Figs. 10 and 17), also occur; they have no 
traces of the planes of the cube or octahedron, a cir¬ 
cumstance which frequently serves to distinguish these 
stones from the vesuvian, which very much resembles 
them. 
Hardness, 7—8 ; specific gravity 3T—4-3. In acids it 
is either quite insoluble, or is only dissolved with great diffi¬ 
culty, silica being separated. The colours are brown-red, 
blood-red, deep-red, yellow, green, black, and white of all 
shades, transparent to opaque, highly lustrous to dim, 
capable of polish. The chemical constituents are silicic 
acid, with magnesia, calcium, protoxide of iron and alumina, 
... f... . 
oxides of iron manganese and chromium, B 3 Si + B Si. 
The transparent finely coloured varieties are called 
precious , the others are called common garnets ; they also 
receive different names from their colours. They are found 
principally in the slaty primary rocks of most countries, 
especially in the mica and blende slates, also in gneiss, 
more rarely in granite, or in volcanic rocks. 
The red transparent garnets are the most highly 
valued, especially if they are large, such as the so-called 
pyrope of Bohemia (Figs. 13, 15), and the Indian amethyst 
coloured (Fig. 14), or the deep red ruby garnet (Fig. 19). 
The yellow ones (Fig. 16) are called topazolites. the apple- 
green (Fig. 17) grossulars, the deep-green (Fig. 12), ouva- 
rovites or uwarowites. 
Figs. 20-24.— The Vesuvian. 
The vesuvian or idocrase has the same composition and 
fusibility as the garnet. It crystallises, however, in quadratic 
prisms, and always contains some water (1*7—3T°/ 0 ); it also 
belongs by preference to the volcanic rocks. 
Besides the simple tetragonal prism, with quadratic 
basal planes, truncations of the lateral edges (Fig. 20), 
of the basal edges (Fig. 21), and of the angles (Fig. 22), 
occur. The colour ranges between brownish-green (Fig. 
23), grass-green (Fig. 22), olive-green (Fig. 21), and 
brown ; the transparency also varies. 
Hardness, 6—6’55 ; specific gravity, 3‘0—3-4 ; vffien 
melted, it is always less (2’95). 
It is soluble in hot acids, which separate the silica in 
the form of a jelly. 
The elements are those of the garnet, in different rela¬ 
tions, however, =3R 3 Si+2BSi, the basis of the first series 
being lime, magnesia, potass, or oxide of iron, that of the 
second alumina, oxide of manganese, iron. 
Is found especially in Piedmont, in Norway, near Fis- 
kum, also in the Fassathal, where the yellow-green varieties 
occur; at Eger in Bohemia, at Egg in Norway, etc. 
The perfectly transparent green, or brownish green 
varieties, are sold as precious stones, under the name of 
Vesuvian gems / they are also called Italian chrysolites , or 
if they are brown, hyacinths ; they may, however, be dis¬ 
tinguished from the real stones of this name by their 
inferior hardness and lustre, as well as by their colour. 
Figs. 25-27.— Chrysolite, Olivine. 
The chrysolite , olivine , or peridote, belongs to a less used 
class of precious stones. It takes on a fine polish, however, 
and has an agreeable pistacio-green colour, which some¬ 
times inclines to a yellow, a brown, or black; it is then 
called common olivine ; and if brownish-black and rich in 
iron, it is called iron-chrysolite or hyalosiderite. 
The primary form is a right rectangular prism (Fig. 
25). This also occurs, however, combined with truncation 
of the lateral and basal edges (Fig. 26), so that the right 
terminal planes almost disappear, and the lateral- planes 
are deeply striated vertically. More frequently it occurs in 
irregular grains or roundish masses, especially in basalt, 
wffiich it characterises. 
The precious chrysolite has the 7° of hardness; the 
common or iron-chrysolite the 5°. The specific gravity 
varies from 2 - 8—3 - 4. 
The chemical constituents are silicate of magnesia, 
with silicate of the protoxide of iron (10 Mg 3 Si + Fe 3 Si.). 
Al m ost, infusible, reducible in borax, however, to a 
green glass, from which salt of phosphorus separates 
silica. 
The pure chrysolite occurs in the East, perhaps in 
Egypt, and is cut as stones for rings in the form of a table ; 
the granular olivine of a yellow-blackish green colour 
occurs especially in the basalts, and, as is worthy of notice, 
in meteoric stones. 
Figs. 28-30.— Epihote, Pistacite. 
This mineral takes its place, from colour and appear¬ 
ance, w r ith the two foregoing. It is, however, not usually 
employed as a pre'cious stone, because it is rarely found 
transparent. The primary form is a right rhomboidal 
prism (Fig. 28) ; the lateral planes of which form angles 
of 115° 24' and 64°.36'; the angles, basal and lateral edges 
also, are frequently truncated, so that very complicated 
forms frequently occur (Figs. 29, 30.) 
The hardness = 6—7’0 ; specific gravity 3’26—3’42. 
Lustre, vitreous; the so-called arendalite is dark-green ; the 
thulite is rose-red; the manganesian epidote of Piedmont 
is reddish-brown; the zoisite from the Fichtel-gebirge is 
grey or white. It can be split in the direction of the 
rhomboidal basal planes, and is friable; when translucent, 
however, it is capable of being polished. The elements 
are silicates of lime and magnesia, protoxide of iron with 
silicate of alumina, and the oxide of iron or manganese 
= 2R 3 Si + A1 (Fe, Mn) Si. 
Is found very frequently in large crystals; for example, 
at Arendal, in Norway, with calcareous spar, in the pri¬ 
mary rocks, namely granite, syenite, serpentine, and mica 
slate; in Piedmont, Dauphine, the Tyrol, near Auerbach, 
on the Bergstrasse, in Pennsylvania, on the Urals, &c. 
Very difficult of fusion, with borax and soda it gives 
the colour of manganese and iron ; insoluble in acids. 
