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.