Part 21

The cat’s-eye is usually cut cabochon or carbuncle-shaped, and the lines (which are due to the fibres of asbestos) are kept in the centre of the stone, and play like the eye of a cat when the stone is moved.

The quartz cat’s-eye is easily distinguished from the oriental of chrysoberyl cat’s-eye, as it is softer and much lighter.

CROCIDOLITE.

Crocidolite or tiger-eye is a light-brown, brownish-yellow to dark-green, and greenish-blue quartz, which has the same chatoyant qualities as the cat’s-eye. When cut cabochon, the crocidolite is called tiger-eye.

This beautiful mineral was very rare some years ago, and good specimens were sold by the carat.

Great quantities, however, have lately been found in South Africa, and although the finest pieces are still used for cameos and intaglios, many objects, such as paperweights, umbrella handles, match-safes, etc., are now cut from this stone.

Crocidolite is often artificially colored to very closely imitate some of the finest shades of the oriental cat’s-eye.

HELIOTROPE.

Heliotrope or blood-stone, as this variety is commonly called, is a dark-green quartz, translucent to opaque, and covered with small red spots or blood-colored blotches, from which the stone derives the name of blood-stone.

This stone has long been used for seal and signet purposes, and many fine intaglios and cameos carved in blood-stone are in existence.

Bucharia, Tartary, Siberia, East India, China, the island of Rum in the Hebrides, the United States, and Canada are some of the places where the heliotrope is found.

CHRYSOPRASE.

The chrysoprase is an apple-green chalcedony, sometimes olive- or whitish-green. It is translucent, scratches glass, and has the specific gravity of 2.56.

The color is due to the presence of oxide of nickel. This stone is found principally in Silesia, but also in Siberia and the United States.

Large pieces of chrysoprase are rare, and even the best specimens lose their color in course of time.

PRASE.

A translucent, spotted leek-green, green quartz, which loses its polish on exposure to the air, is known as prase.

This stone is found principally in the iron mines of Brietenbaum, Saxony, and also in Brittany, the Tyrol, Scotland, Salzburg, Finland, and the United States.

Prase is sometimes known commercially as “mother of emerald,” and a greenish crystalline quartz is also often called prase.

PLASMA.

Plasma is a dark grass-green quartz, feebly translucent, and is sometimes covered with white or yellow spots. Plasma is somewhat lighter in weight than the heliotrope and does not take as fine a polish.

This stone is found in India, China, and in the Black Forest, Germany.

CHALCEDONY.

Chalcedony is cloudy or translucent, white, yellowish-gray, blackish-brown, light to dark-blue, milky-white, and black.

This quartz is sometimes nearly transparent, waxy in lustre, and in some varieties has a light gray and transparent base with dark cloudy spots. This last variety is called “cloudy chalcedony”. Another kind, with gray and white stripes alternating, is known as chalcedonyx.

Iceland, the Faroe Islands, Hüttenberg, Loben, Saxony, Hungary, Nubia, Nova Scotia, Oberstein, Ceylon, India, Siberia, Carinthia, the Hebrides, the United States, and Canada are places where chalcedony is found.

AGATES.

Agate is an improved variety of chalcedony and comprises the following kinds.