All About the Properties of Cyanite and Lapis Lazuli

CYANITE.

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.

LAPIS LAZULI.

Lapis lazuli, the sapphire of the ancients, is a mineral, translucent to opaque, ranging in color from colorless to an azure-blue, violet-blue, green, and red.

The principal color, however, is a rich, azure blue, sometimes shading into green, and having a vitreous to greasy lustre.

Its hardness is 5 to 5.5, specific gravity 2.38 to 2.42; it is decomposed by muriatic acid, and fuses before the blow-pipe to a white glass. It is rarely found clean, but has usually a number of veins and spots of a metallic nature. It is composed of:

Silica 45.

Alumina 31.76

Soda 9.09

Lime 3.52

Sulphuric acid 5.89

and traces of iron, soda, and potash.

This mineral is found in Siberia, Transylvania, Persia, China, Thibet, Tartary, South America, India, and Brazil.

Lapis lazuli is sometimes employed for jewelry, and was for some centuries ground up and used to make the mineral paint known as genuine ultramarine. This paint is now produced chemically, and the more costly mineral compound is rarely used.