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Encyclopedia Britannica - Main :: INV-JED |
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JADE , a name commonly applied to certain ornamental stones, mostly of a green colour, belonging to at least two distinct species, one termed nephrite and the other jadeite. Whilst the term jade is popularly used in this sense, it is now usually restricted by mineralogists to nephrite. The word jade' is derived (through Fr. le jade for l'ejade) 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 reputed value of the stone in renal diseases is also suggested by the term nephrite (so named by A. G. Werner from Gr. vechpos, kidney), and by its old name lapis nephriticus. Jade, in its wide and popular sense, has always been highly prized by the Chinese, who not only believe in its medicinal value but regard it as the symbol of virtue. It is known, with other ornamental stones, under the name of yu or yu-chi (yustone). According to Professor H. A. Giles, it occupies in China the highest place as a jewel, and is revered as " the quintessence of heaven and earth." Notwithstanding its toughness or tenacity, due to a dense fibrous structure, it is wrought into complicated 1 The English use of the word for a worthless, ill-tempered horse, a " screw," also applied as a term of reproach to a woman, has been referred doubtfully to the same Spanish source as the O. Sp. ijadear, meaning to pant, of a broken-winded horse. forms and elaborately carved. On many prehistoric sites in Europe, as in the Swiss lake-dwellings, celts and other carved objects both in nephrite and in jadeite have not infrequently been found; and as no kind of jade had until recent
interest
Nephrite, or true jade, may be regarded as a finely fibrous or compact variety of amphibole, referred either to actinolite or to tremolite, according as its colour inclines to green or white. Chemically it is a calcium-magnesium silicate, CaMg3(SiO3)4. The fibres are either more or less parallel or irregularly felted together, rendering the stone excessively tough ; yet its hardness is not great, being only about 6 or 6.5. The mineral sometimes tends to become schistose, breaking with a splintery fracture, or its structure may be horny. The specific gravity varies from 2.9 to 3.18, and is of determinative value, since jadeite is much denser. The colour of jade presents various shades of green, yellow and grey, and the mineral when polished has a rather greasy lustre. Professor F. W. Clarke found the colours due to compounds of iron, manganese and chromium. One of the most! famous localities for nephrite is on the west side of the South Island of New Zealand, where it occurs as nodules and veins in serpentine and talcose rocks, but is generally found as boulders. It was known to the Maoris as pounamu, or " green stone," and was highly prized, being worked with great labour into various objects, especially the club-like implement known as the mere, or pattoo-pattoo, and the breast ornament called hei-tiki. The New Zealand jade, called by old writers " green talc of the Maoris," is now worked in Europe as an ornamental stone. The green jade-like stone known in New Zealand as tangiwai is bowenite, a translucent serpentine with enclosures of magnesite. The mode of occurrence of the nephriteandboweniteof New Zealand has been described by A. M. Finlayson (Quart. Jour. Geol. Soc., 1909, p. 351). It appears that the Maoris distinguished six varieties of jade. Difference of colour seems due to variations in the proportion of ferrous silicate in the mineral. According to Finlayson, the New Zealand nephrite results from the chemical alteration of serpentine, olivine or pyroxene, whereby a fibrous amphibole is formed, which becomes converted by intense pressure and movement
Nephrite occurs also in New Caledonia, and perhaps in some of the other Pacific islands, but many of the New Caledonian implements reputed to be of jade are really made of serpentine. From its use as a material for axe-heads, jade is often known in Germany as Beilstein (" axe-stone "). A fibrous variety, of specific gravity 3.18, found in New Caledonia, and perhaps in the Marquesas, was distinguished by A. Damour under the name of " oceanic jade. Much of the nephrite used by the Chinese has been obtained from quarries in the Kuen-lun mountains, on the sides of the Kara-kash valley, in Turkestan. The mineral, generally of pale colour, occurs in nests and veins running through hornblende-schists and gneissose rocks, and it is notable that when first quarried it is comparatively soft. It appears to have a wide distribution in the mountains, and has been worked from very ancient times in Khotan
Jade implements are widely distributed in Alaska and British Columbia, being found in Indian graves, in old shell-heaps and on the sites of deserted villages. Dr G. M. Dawson , arguing from the discovery of some boulders of jade in the Fraser river valley, held that they were not obtained by barter from Siberia, but were of native origin; and the locality was afterwards discovered by Lieut. G. M. Stoney. It is known as the Jade Mountains, and is situated north of Kowak river, about 15o miles from its mouth. The study of a large collection of jade implements by Professor F. W. Clarke and Dr G. P. Merrill proved that the Alaskan jade is true nephrite, not to be distinguished from that of New Zealand.radeite is a mineral species established by A. Damour in 1863, differing markedly from nephrite in that its relation lies with the pyroxenes rather than with the amphiboles. It is an aluminium sodium silicate, NaAl(SiO3),, related to spodumene. S. L. Pen-field showed, by measurement, that jadeite is monoclinic. Its colour is commonly very pale, and white jadeite, which is the purest variety, is known as " camphor jade." In many cases the mineral shows bright patches of apple-green or emerald-green, due to the presence of chromium. Jadeite is much more fusible than nephrite, and is rather harder (6.5 to 7), but its most readily determined character is found in its higher specific gravity, which ranges from 3.20 to 3.41. Some jadeite seems to be a metamorphosed igneous rock. The Burmese jade, discovered by a Yunnan trader in the 13th century, is mostly jadeite. The quarries, described by Dr F. Noetling, are situated on the Uru river, about 12o m. from Mogaung, where the jadeite occurs in serpentine, and is partly extracted by fire-setting. It is also found as boulders in alluvium, and when these occur in a bed of laterite they acquire a red colour, which imparts to them peculiar value. According to Dr W. G. Bleeck, who visited the jade country of Upper Burma after Noetling, jadeite occurs at three localities in the Kachin HillsTawmaw, Hweka and Mamon. The jadeite is known as chauk-sen, and is sent either to China or to Mandalay, by way of Bhamo, whence Bhamo has come erroneously to be regarded as a locality for jade. Jadeite occurs in association with the nephrite of Turkestan, and possibly in some other Asiatic localities. In certain cases nephrite is formed by the alteration of jadeite, as shown by Professor J. P. Iddings. The Chinese feits'ui, sometimes called " imperial jade," is a beautiful green stone, which seems generally to be jadeite, but it is said that in some cases it may be chrysoprase. It is named from its resemblance in colour to the plumage of the kingfisher. The resonant character of jade has led to its occasional use as a musical stone. In Mexico, in Central America and in the northern part of South America, objects of jadeite are common. The Kunz votive adze from Oaxaca, in Mexico, is now in the American Museum of Natural History, New York
Chooromelanite is Damour's name for a dense, dark mineral which has been regarded as a kind of jade, and was used for the manufacture of celts found in the dolmens of France and in certain Swiss lake-dwellings. It is a mineral of spinach-green or dark-green colour, having a specific gravity of 3.4, or even as high as 3.65, and may be regarded as a variety of jadeite rich in iron. Chloromelanite occurs in the Cyclops Mountains in New Guinea, and is used for hatchets or agricultural implements, whilst the sago-clubs of the island are usually of serpentine. Sillimanite, or fibrolite, is a mineral which, like chloromelanite, was used by the Neolithic occupants of western Europe, and is sometimes mistaken for a pale kind of jade. It is an aluminium silicate, of specific gravity about 3.2, distinguished by its infusibility. The jade tenace of J. R. Haiiy, discovered by H. B. de Saussure in the Swiss Alps, is now known as saussurite. Among other substances sometimes taken for jade may be mentioned prehnite, a hydrous calcium-aluminium silicate, which when polished much resembles certain kinds of jade. Pectolite has been used, like jade, in Alaska. A variety of vesuvianite (idocrase) from California, described by Dr. G. F. Kunz as californite, was at first mistaken for jade. The name jadeolite has been given by Kunz to a green chromiferous syenite
pink
An exhaustive description of jade will be found in a sumptuous work, entitled Investigations and Studies in Jade (New York
illustration
presented by him to the Metropolitan Museum of Art, New York. The work, which is in two folio volumes, superbly illustrated, was printed privately, and after loo copies had been struck off on American hand-made paper, the type was distributed and the material used for the illustrations was destroyed. The second volume is a catalogue of the collection, which comprises 900 specimens arranged in three classes: mineralogical, archaeological and artistic. The important section on Chinese jade was contributed by Dr S. W. Bushell, who also translated for the work a discourse on jadeYii-shun by T'ang Jung-tso, of Peking. Reference should also be made to Heinrich Fischer's Nephrit and Jadeit (2nd ed., Stuttgart, 188o), a work which at the date of its publication was almost exhaustive. (F. W. R.*) End of Article: JADE If you wish, you can link directly to this article.
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