Axinite.
Reading edition
Axinite is a brittle mineral which has occasionally furnished some pretty gem stones.
The hardness of this stone is 6.5 to 7; specific gravity, 3. to 3.3; lustre, vitreous. It is transparent to translucent, is not attacked by acids, and melts readily before blow-pipe. It is composed of:
Silica 43
Lime 20
Alumina 16
Ferric oxide 10
Boron trioxide 5
Manganese dioxide 3
Magnesia 2
Potash 1
Axinite occurs in clove-brown, plum-blue, and pearl-gray, and exhibits trichroism. The best specimens come from St. Christophe in Dauphiny, but it is also found at Santa Maria, and in Switzerland, Sweden, England, Chili, Saxony, the Hartz Mountains, and the United States.
Axinite is usually cut, like the opal, cabochon, but is rarely used as a gem stone.