This stone is the transparent variety of disthene, and is sometimes
commercially known as sappare. Cyanite is colorless to bluish-white,
sky-blue, berlin blue, yellowish- and reddish-white, gray, and green.
The hardness is 5 to 7, specific gravity 3.45 to 3.70, lustre vitreous
and pearly; it is infusible before the blow-pipe, but fuses with borax;
is not attacked by acids, and is composed of:
Silica 36.8
Alumina 63.2
Cyanite is found in Switzerland, the Tyrol, Styria, Carinthia, Bohemia,
Norway, Finland, France, South America, Scotland, Ireland, Siberia, the
East Indies, and the United States. Clean specimens are not plentiful,
and fine blue pieces have frequently been sold for sapphires. The
cyanite can be distinguished from the sapphire by its inferior hardness
and lighter weight.