Jade
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- Information about Thomas Biskup's roguelike game can be found at JADE. Also Jade Villalon, a Final Fantasy singer.
Jadestein.jpg
An ornamental stone, jade is a name applied to two different silicate minerals. Nephrite is a form of the amphibole actinolite (a mineral that also includes a form of asbestos). The second, the mineral jadeite, is a pyroxene. Nephrite has the formula Ca2(Mg, Fe)5Si8O22(OH)2. Jadeite has the formula NaAlSi2O6. The two are quite similar in appearance and it wasn't until 1863 that the two forms of this gemstone were distinguished.
It is an exceptionally tough material, and was first used for things such as axe heads, knives, and weapons. Later, as other materials could replace jade as a weapons material, it became appreciated for its beauty.
Nephrite can be found in a creamy white form as well as a green color, while jadeite shows more color variation. Of the two, jadeite is rarer, and is the form of jade mostly used in Central America. Nephrite jade was used mostly in China and New Zealand.
Jade is the official gemstone of British Columbia.
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History
During Neolithic times, the key known sources of nephrite jade in China for utilitarian and ceremonial jade items were the now depleted deposits in the Ningshao area in the Yang Ze River delta (Liangzhu Jade culture 3400–2250 BC) and in an area of the Liaoning province in Inner Mongolia (Hongshan Culture 3500–2200 BC). Jade was used to create many utilitarian and ceremonial objects, ranging from indoor decorative items to jade burial suits. From about the earliest Chinese dynasties until present, the jade deposits in most use were from the region of Khotan in the Western Chinese province of Xinjiang. There, white and greenish nephrite jade is found in small quarries and as pebbles and boulders in the rivers flowing from the Kuen-Lun mountain range northward into the Takla-Makan desert area. River jade collection was concentrated in the Yarkand, the White Jade (Yurungkash) and Black Jade (Karakash) Rivers. From the Kingdom of Khotan, on the southern leg of the Silk Road, yearly tribute payments consisting of the most precious white jade were made to the Chinese Imperial court and there transformed into objets d'art by skilled artisans as jade was considered more valuable than gold or silver.
Jadeite with its bright emerald-green, pink, lavender and brown colors was imported from Burma to China only after the 17th century and became known as Feitsu or Kingfisher (feathers) Jade.
In New Zealand, where it is known as greenstone or pounamu, nephrite was fashioned for centuries by Maori to make weapons and ornaments, and is still widely used to make carved jewellery although the mining of it is restricted and closely monitored.
Faux Jade
Many minerals are sold as jade. Some of these are: serpentine (also bowenite), carnelian, aventurine quartz, glass, grossularite, Vesuvianite and soapstone. "Korean jade," "Suzhou jade," "Styrian jade" and "New jade" are all really serpentine. Other names of fake jade are: "Honan jade," "Metajade" and "Sinkiang jade."
Real jade may be enhanced (sometimes call "stabilized"). One method involves bleaching a promising but stained piece of jadite. The stone is then impregnated with a form of plastic. The result is called "B" jade. Currently, infrared spectroscopy is the only test for the detection of polymer in jadite.
The red color of Red jade can be enhanced with heat. The effects are somewhat uncontrollable and may result in a dull brown. In any case, translucency is usually lost.
See also
Further Reading
- Laufer, Berthold. 1912. JADE: A Study in Chinese Archaeology & Religion. Reprint: Dover Publications, New York. 1974.
External links
- Jade (http://mineral.galleries.com/minerals/gemstone/jade/jade.htm)
- Jade: Chinese Stone of Heaven (http://www.gemstone.org/gem-by-gem/english/jade.html)
- ancient chinese jade (http://www.comp.nus.edu.sg/~yuenck/hist/jade.htm)de:Jade (Mineral)