Part 15

Vermeille is a name given to the orange-red almandine, Cape garnet to the bright red-yellow variety, Cape ruby to the pyrope, and American ruby to the blood-red kind found in New Mexico, Montana, and Arizona. Carbuncle is a term applied to all garnets cut with a smooth rounding top, sometimes called, after the French, cabochon.

Uwarowite or lime-chrome garnet is one of the rarest and most beautiful of the garnet group.

The color of this stone is emerald-green, hardness 7.5, and specific gravity 3.41 to 3.52. Uwarowites are found near Bissersk in the Urals of Russia, but rarely in specimens of sufficient size to cut into gems.

This garnet is heavier and harder than the true emerald.

Demantoide or Bobrowska garnet is a soft garnet, olive-green to brown and blackish-green in color, sometimes light green. It is found in the Bobrowska River in the Urals. The specific gravity is 3.85, and hardness about 6, its softness making it undesirable for many ornaments. Before the blow-pipe it fuses into a black bead.

These garnets are often sold as olivines; they are heavier than olivines and softer.

Demantoide is composed of:

Silica 35.44 Lime 32.85 Sesquioxide of iron 32.85 Magnesia .20

TOPAZ.

Topaz belongs to the rhombic system of crystallization. Its cleavage is basal and perfect, fracture uneven, hardness 8, scratching quartz distinctly, specific gravity 3.4 to 3.6, lustre vitreous, refraction double, and colors ranging from colorless or white to bluish-white, light blue, wine-yellow, straw-yellow, golden-yellow, greenish- and pale-red to pink.

Topaz becomes electric from rubbing or pressure, and retains electricity for twenty-four hours. Before the blow-pipe topaz partly loses color, but does not melt, and with borax it fuses slowly to a white bead.

Topaz is partially attacked by sulphuric acid, and dissolves in salts of phosphorus.

The composition of topaz is:

Silicon 15.05 Aluminium 30.02 Oxygen 36.08 Fluorine 17.05

Goutte d’eau or colorless topaz, sometimes called “slaves diamond,” Siberian or bluish-white, Brazilian or golden to reddish-yellow, Saxony or pale-wine yellow, Brazilian ruby or pink, Brazilian sapphire or light blue, and aquamarine or greenish, are the various commercial names for topaz.

Most of the Brazilian rubies or pink topazes are produced by heating the reddish or dark-yellow variety, either in a crucible or by enveloping the stone in German tinder and setting fire to the tinder. If heated too much, the stone is apt to become colorless, and if suddenly cooled it may crack.

Colorless or white topaz takes a very high polish, and is wonderfully clear and transparent.

The great Portuguese diamond, “The Braganza,” of about 1,680 carats, is supposed to be a white topaz.

Topaz is found in the Urals, Kamschatka, Alabaschka, Miask, Nestschinsk, Adun Tschilon, Villa Rica, Boa Vista, Capao, Lana, Minas Novas, Cairngorm Mts., Schlackenwald, Zinnwald, Schneckenstein, Ehrenfriedensdorf, Altenburg, Orenburg, Mourne Mts.—Ireland, Australia, New South Wales, Ceylon, Mexico, and the United States. False topaz, or the ordinary topaz of commerce, is yellow quartz resembling yellow topaz, but lacking its brilliancy and hardness; it is also very much lighter, being only 2.5 to 2.7 in specific gravity.

Beryl and chrysolite are often mistaken for topaz, but as they are softer and beryl is much lighter, they are easily distinguished from the topaz. The strong electric property of the topaz is also a conclusive test.

Oriental topaz, or yellow corundum, is harder and heavier than the occidental or true topaz.

APATITE.

Apatite, which is seldom used as a gem stone, sometimes resembles the beryl and emerald, but is much softer and rarely has the color and brightness combined of the former gems.

This mineral, composed principally of subsesquiphosphate of lime, is 4.5 to 5. in hardness, has the specific gravity of 2.95 to 3.25, is transparent to opaque, vitreous in lustre, infusible before the blow-pipe, and dissolves slowly in nitric acid. In colors, apatite varies from colorless to sea-green, bluish-green, violet-blue, gray, yellow, red, and brown.

Apatite is found in Saxony, the Hartz Mts., Bohemia, Norway, Bavaria, England, St. Gothard in Switzerland, and in the United States.

FELSPAR.

Four varieties of felspar are used as gem stones—moonstone or orthoclase, sunstone or avanturine felspar, Amazon stone or green felspar, and Labrador or Labrador spar.

MOONSTONE.