13 
in the oxyhydrogen flame, especially when it is reduced to 
powder. During the process, it first becomes opaque, then 
rounded at the angles and edges, and finally disappears. 
It then unites with two equivalents of oxygen, and forms 
carbonic acid, which disappears, proving that, like graphite, 
it consists of pure carbon. We recognise, therefore, in the 
diamond only one of the many elements of which the body 
of the earth consists, and that in the purest form, as a 
metalloid, like sulphur, iodine, and selenium. 
The diamond was well known to the ancient Jews, 
Arabians, Greeks, and Romans, by whom it was obtained 
from India, where it occurs near Purstal, between Hydera¬ 
bad and Masulipatam. There are other localities, Perma 
in Bundelcund, Ellora, and near Pontiana in Borneo. It 
is also found at Minas Geraes in Brazil, Bahia, Australia, 
Rutherford in North Carolina, the Urals, and at Constan¬ 
tine in North Africa. It is generally found loose in the 
sand, especially along with gold dust, as is shown in an 
example in the British Museum, which possesses a speci¬ 
men of a crystal attached to alluvial gold. In Brazil it 
has been found in itacolumite or flexible sandstone, a stone 
composed of granular quartz and plates of mica. 
It is obtained from the sand in several localities and 
in certain layers, by washing like gold. 
Rough diamonds are for the most part crystallised and 
isolated, rarely worn to roundish, highly-!ustrous grains 
The crystals usually present curved surfaces, striated in 
certain directions (Figs. 4 and 5), and are sometimes twins. 
They can all be split in the direction of the planes of the 
octahedron. 
The cutting is effected by means of iron plates, with 
the help of powdered diamonds and a little water or oil. 
They are for the most part small, and vary from the 
size of a millet seed to that of a pigeon’s egg and larger, so 
that one even the size of a pea is a rarity. 
The value varies with the purity of colour, trans¬ 
parency, and size, but not usually in a fixed ratio. A 
brilliant of one carat in weight costs eight guineas in 
England, one of two carats, of corresponding quality, is 
worth about 48 guineas; in those of twenty carats and 
upwards, the value increases at a higher ratio. 
Cut diamonds are distinguished as— 
1. Table stones , which more or less resemble Figs. 13 
and 14, Plate II., bounded by rectangles, rhomboids, and 
trapeziums, flat on their upper and under surfaces. 
2. Hose diamonds (v. Plate II. Figs. 14 and 15), flat 
below, curved above, and provided with six star-like tri¬ 
angular surfaces grouped together, which in larger stones 
are surrounded by twelve other similar facettes, sometimes 
they are irregular, oblong, etc., as is seen especially in old 
ornaments. 
3. Brilliants of the form of an octagon, truncated above 
to a greater degree than on their under surface. The 
upper pyramid is called the crown or culasse, the lower 
the calette. The edges are so provided with rhombic 
faces and triangles, that the basal edges are sharpened, 
and the lateral edges facetted, as is distinctly seen in Fig. 
6, Plate I. These are most highly valued, and show to the 
greatest advantage the above-mentioned play of colours. 
4. Bound or button-shaped stones, as is represented 
in Plate I. Figs. 7-9, were formerly cut only in large frag¬ 
ments, and for certain objects. The genuineness of the 
diamond is best ascertained from its hardness ; it must be 
able to scratch the ruby and corundite, which neither the 
white topaz, nor still less flint-glass can do; the lustre 
and play of colours are also means of recognising it. 
Figs. 10-16.— Corundite (Sapphire and Ruby). 
The corundite is the hardest stone next to the dia¬ 
mond, and is scratched by it alone, while it can scratch 
all other stones, with the exception of the diamond. It 
consists, in its pure condition, of alumina only; coloured 
specimens contain traces of the oxides of iron and manga¬ 
nese, silica, and the like. The specific gravity varies 
from 3‘9—140. We distinguish between noble and com¬ 
mon corundum. To the former belong the ruby and 
sapphire, to the latter the diamond-spar and emery. 
The form of the crystal is a rhombohedron, Fig. 10; 
there are, however, usually found combinations of the 
rhombohedron with hexagonal prisms, or these alone, as 
in Fig. 13, and also six-sided double pyramids. 
The ruby , or deep-red corundite, Fig. 15, is the most 
valuable of all; it occurs of the finest quality in lower 
India and in Ceylon. The rough carat is valued at from 
£3 to £4. A ruby of two carats’ weight, however, if 
perfect in colour and transparency, is more valuable than 
a diamond of the same weight, because it is much more 
rare. The sapphire, or blue corundite, Fig. 16, occurring 
from a clear to a dark blue, costs 30s. to 50s. and is also 
found in India, particularly in Ava, in Ceylon, Brazil, Bo¬ 
hemia and France, also at the Laacher-Sea, in Prussia. 
The diamond-spar or bort is an impure corundite, 
which is used for polishing diamonds, and other precious 
stones; it comes from China, and costs from 20s. to 22s. 
a carat. The compact granular corundum is known by 
the name of emery , and is obtained chiefly from Naxos; 
it is, however, also found near Schwarzenberg in the 
Erzgebirge of Saxony, and is used for the cutting and 
polishing of glass, stones, etc. 
Figs. 17-21.— Chrysoberyl (Cymophane, Alexandrite). 
Right rhombic, in low prisms or tables, or in combi¬ 
nations of twins, with truncation of the acute or obtuse 
lateral edges, which form angles of 129° 38'. Hardness 
= 8*5, a little less than that of the corundum; specific 
gravity = 3’5—3 - 8. 
Composition; alumina 78*91, glucina 18"02, oxide of 
iron 3H2, frequently with traces of the oxide of chromium. 
Soluble in no acid, infusible before the blowpipe, gives 
with borax a greenish bead, from which salt of phosphorus 
does not separate silica. When polished, it is used as an 
ornament, and takes on a very fine polish. Yellow, green, 
and red; the yellowish-green, with play of golden lustre, 
is the most valuable. Is found in the primary formations, 
in granite, gneiss, and mica slate, in Moravia, Connecticut, 
and Siberia. 
Figs. 22 and 23.— Spinel. 
The primary form is a regular octagon, as seen in Fig. 
22, and at the same time is of most frequent occurrence; 
