Phenacite.
This mineral, rarely used as a gem stone, is 7.5 to 8 in hardness; specific gravity, 2.96 to 3; lustre, vitreous; transparent to semi-translucent, doubly refractive, it does not melt before the blow-pipe, and contains:
| Silica | 54.2 |
| Glucina | 45.8 |
Phenacite occurs colorless, and also bright wine-yellow inclining to red, and brown. This stone is found in Russia, Mexico, and Alsace.
The colorless or transparent variety approaches the diamond in brilliancy, especially under artificial light.
Epidote.
Epidote usually occurs in a peculiar yellowish-green, called pistachio green, a color that is seldom found in other minerals. Besides this color, olive, brownish-green, greenish-black and black, red, yellow-gray, and grayish-white occur. The hardness of epidote is 6 to 7; specific gravity, 3.32 to 3.50; lustre, vitreous to pearly; refraction, double. The stone is transparent to opaque, is attacked by acids, and is slightly affected by the blow-pipe. It is composed of:
| Silica | 38 |
| Alumina | 22 |
| Ferric oxide | 15 |
| Lime | 23 |
| Water | 2 |
Epidote is found in Norway, Saxony, Siberia, Brazil, on the St. Gothard, in Switzerland, in the Tyrol, and in the Hartz.