JADE, a name applied to certain minerals of compact texture and colour varying from nearly white to dark green which have been used from prehistoric times in the manufacture of weapons, utensils and ornaments. The name is often restricted to two minerals, jadeite and nephrite. The word jade is derived (through Fr. le jade, for re jade) from Span. ijada (Lat. ilia), the loins, this mineral having been known to the Spanish conquerors of Mexico and Peru under the name of piedra de ijada or yjada (colic stone). The superstitions of the Mexicans regarding the stone were perpetuated in the Old World. When powdered and mixed with water it was supposed a powerful remedy for all kinds of internal disorders, to strengthen the frame and prevent fatigue, to prolong life and if taken in sufficient quantities just before death to prevent decomposition.
Jadeite is essentially a silicate of aluminium and sodium but generally contains small quantities of iron, calcium and magnesium. In the variety called chloromelanite, the iron amounts to i o%. In chemical composition and crystalline characters jadeite belongs to the pyroxene group of minerals and its chemical formula is therefore written It occurs very rarely in distinct crystals, though two small specimens were obtained from the Heber Reginald Brooke Collection of suffi cient size to allow of morphological and optical investigation. Its hardness is 7 and specific gravity 3.33 ; it fuses in the blowpipe flame.
Nephrite is a silicate of calcium and mag nesium, generally having a little iron re placing the magnesium. It belongs to the amphibole group of minerals and is identi cal in composition with actinolite and tremolite of that species, which have the formula Its hardness is 6 and specific gravity 3.o, and it has a lower melting point than jadeite.
Both jadeite and nephrite are very tough, owing to the way in which the con stituent fibres interlace. This toughness is very well illustrated in the case of nephrite by the fact that a pressure of 5o tons was required to crush certain cubical pieces of one inch size: large pieces can often only be broken by heating and then rapidly cooling by immersion in water. Suitably cut jade possesses the property of emitting a very clear musical tone when struck and of maintaining the vibrations for a comparatively long time. This has led to its use in the manufacture of bells and sounding plates and tubes. The colours which are very varied passing from black through brown to green and white are chiefly due to iron oxides and silicates and to some extent to chromium. Because of similarity in external appearance a num
ber of minerals are often confused with jade and among these are included saussurite, bowenite, californite and verdite.
The Chinese value jade above all precious stones, as is indi cated by the following quotation from T'ang Jung-tso in a dis course on jade: "The magic powers of heaven and earth are ever combined to form perfect results: so the pure essences of hill and water become solidified into precious jade." The Chinese word yu and the Japanese equivalents represent not only jade and gems in general, but signify the five cardinal virtues, charity, modesty, courage, justice and wisdom.
In spite of its toughness jade is worked into complicated forms and elaborately carved. This is done principally in China, where most beautiful specimens have been found. On many pre historic sites in Europe, as in the Swiss lake-dwellings, celts and other carved objects both in nephrite and jadeite have been found; and as no kind of jade had until recent years been dis covered in situ in any European locality, it was bilieved that either the raw material or the worked objects must have been brought by some of the early inhabitants from a jade locality probably in the East. The discovery of native jade in Europe was, therefore, very important—nephrite was found in Silesia and jadeite in the Alps, whilst pebbles of jade were found in Austria and north Germany—and proved that the jade imple ments were not of exotic origin.
Jadeite is found in several places in upper Burma, notably in the Mogaung district and in the Kachin hills. The export trade to China, which absorbs practically the whole of the output, is exceedingly valuable and is worth nearly as much as the produce of the ruby mines. Jadeite is found in Tibet and in China in the provinces of Shensi and Yunnan.
Nephrite occurs in New Zealand, particularly in the South island, in New California, in Siberia at Batugol, Lake Baikal, in Alaska and many places in China. The Chinese derive their main supply from places near the southern boundary of Eastern Tur kestan, especially from the valleys of the rivers Karakash and Yarkand and the Kuen Lun range of mountains.
See H. Fischer, Nephrit and Jadeit (Stuttgart, 188o) ; H. R. Brooke, Investigation and Studies in Jade (privately printed, New York, 1906) ; G. F. H. Smith, Gem-stones (London, 1926).
(W. A. W.)