Jade is a name applied to about 150 varieties of ornamental stones, but should be properly restricted to the mineral Nephrite (q.v.), so called from the Greek nephros because it was supposed by the ancients to have virtue in renal diseases. The name is from the Spanish ijada, 'the flank' (from the Latin ilia), because it was believed to cure pain in the side; and the mineral was brought by the Spaniards from Mexico. True jade is a native silicate of calcium and magnesium, tough, and of various shades of green, yellowish-gray, and greenish-white. It is never crystalline, and it is very hard, but not excessively so, and is remarkable for being less hard when freshly broken than after exposure. The specific gravity varies from 2·91 to 3·06. Jade has been reported in isolated cases in Prussia, Turkey, and Corsica, but important deposits are unknown in Europe. It is principally found in China, Siberia, New Zealand, and in some of the islands of the South Pacific, while its occurrence has also been reported in British Columbia and Alaska. Although jade ornaments were brought by the Spaniards from Central and South America, the mineral is not found there in situ. It is doubtful, moreover, if the majority of these reputed jade ornaments were of true jade. The 'Amazon-stone,' for instance, is not, but is a variety of microcline feldspar, while the 'Bowenite' of North America is really a variety of serpentine. Many objects exported from China as of jade are really of serpentine. A variety of jade found in New Caledonia and the Marquesas is known as 'Oceanic jade,' differing from the oriental variety in the proportions of lime and magnesia. The New Zealand jade also differs from the Asiatic, and many of the stones used by the Maoris known as kawa-kawa do not contain some of the inseparable ingredients of true jade. The real jade found in New Zealand is known to the Maoris as the punamu or 'green-stone,' and is found along the west coast of the south island. They work it into amulets, ornaments, and even axe-heads on account of its hardness. In New Caledonia and some of the other Pacific islands jade is also used for axe-heads, and thus has become known to mineralogists as axe-stone.
Nowhere is jade found so extensively and prized so highly as in China. And yet a good deal of the so-called China jade is really jadeite—which is a silicate of alumina and sodium, and therefore a different chemical compound from true jade. Jadeite has a brighter colour, and is harder than jade, while its sp. gr. ranges from 3·28 to 3·35. Jadeite is also found in Burma, near Bhamo, and is doubtless the substance of which many of the old Mexican and Central American ornaments were made. An Egyptian scarabæus in jadeite has been found, and axes of jadeite have been discovered in the lake-dwellings of central Europe, although the mineral itself is unknown in Europe.
In China jade is most ingeniously and elaborately carved. It is called Yu-chi, or 'yu-stone,' and has for ages been obtained from the Kuen-lun Mountains, where it is found in veins among the schistose and gneissose rocks of the Kura-kash, and the south of the Khotan province. Jade from that district has been known to the Chinese for over two thousand years. Very fine dark-green jade is found near Batougol, in Siberia, in boulders.
The mines of Chinese Turkestan are, so far as is known, the only mines which are regularly worked. There are over one hundred of them, riddling one large mountain-side with dark tunnels, giving access to long galleries winding in all directions; in some cases piercing right through to the other side of the mountain. The mineral is found in veins several feet in thickness, but so full of fissures that perfect blocks are not often found of more than a few inches thick. It is for this reason that large pieces are so valuable, and are usually reserved for the imperial tribute. At Canton there is a great jade market, where the mineral itself as well as all sorts of articles made from it are on sale. The ornaments are mostly bracelets, brooches, ear-rings, finger-rings, and hairpins, and these are as dear to the Chinese ladies as diamonds are to their Caucasian sisters. A necklace of green jade beads will cost £1000; two buttons suitable for a mandarin will fetch £30; while for a moderate-sized piece of the vivid green, which is much sought after, from £500 to £600 will be paid. The stone is exceedingly difficult to work, and hence the great cost of carved specimens; but even at Monien a pair of rough bracelets, not of the finest quality, will fetch £20 or £30.
Jade ornaments have been found among the lake-dwellings of Switzerland—at the lakes of Bienne, Zurich, and Pfäffikon; stone celts have been found in dolmens in France which resemble jadeite, but with a larger proportion of iron, and are now known as chloromelinite; and implements of the Neolithic age in western Europe, once supposed to be of jade, are now recognised as of fibrolite (a silicate of aluminium, sp. gr. 3·2).
There is no natural jade among the rock formations of Switzerland, so that the ornaments of the lake-dwellers must either have been brought by their ancestors from Asia, or have been obtained in barter from some of the nomadic races of prehistoric times. Dr Schliemann reported jade celts among the ruins at Hissarlik, and in the British Museum there is a seal-cylinder of jade among the Assyrian and Babylonian relics. The jade ornaments of India must have been brought from central Asia.
See Fischer, Nephrit und Jadeit (2d ed. Stuttgart, 1881); Meyer's Catalogue of Jade Articles in Dresden Museum (Leip. 1882-83); and Miss Gordon-Cumming's Wanderings in China (1885).