JADE, an ornamental stone, of which there appear to be two varieties, common jade or nephrite, and saussurite or jade tenace. Common jade is a silicate of magnesia, oxide of iron, and alumina. Its specific gravity varies from 2.9 to 3.0; hardness 7.0. Its colour is leek green, passing into grey. It is very tough, and scarcely fusible before the blow-pipe. Nephrite was formerly worn as a charm, and was supposed to be a cure for diseases of the kidney, whence the name from répos, kidney. From its toughness it has been used for the blades of hatchets by the New Zealanders, and other savage nations. Humboldt speaks of jade stones being an article of trade among the natives of the N. and S. sides of the Oroonoko. Jade is much used in Turkey and Poland for the handles of knives, daggers, swords, &c.; and in India, ornaments and trinkets, delicately worked, are made of it. In China, the jade is of a whitish colour, and is called yu. It is formed into vases, rings, and other articles. A great variety of jade ornaments from India and China appeared at the Great Exhibition of 1851. Such articles are very costly, on account of the extreme difficulty of working this refractory substance, but it has been suggested that mortars, pestles, and some other objects required by chemists, could be manufactured of jade of larger size than can now be made of agate, and, from the simplicity of the forms, at moderate cost. Jade is polished like carnelian, but it takes only a greasy, not a brilliant polish. Saussurite is a double silicate of magnesia, lime, and
oxide of iron, with silicate of alumina; specific gravity 3.2 to 3.4, hardness 5.5. Its colour is greenish-white, or ashy-grey; its cleavage is in two directions, meeting at an angle of nearly 120°. Its lustre is pearly, resinous, or vitreous; it is extremely tough, and is fusible before the blow-pipe. (c. r.)