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. Jade has a Mohs hardness of between 6.5 and 7.0 ^*.

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, Myanmar and New Zealand.

Jade is the official gemstone of British Columbia, where it is found in large deposits in the Lillooet and Cassiar regions.

History

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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 Yangtze River Delta (Liangzhu jade culture 3400–2250 BC) and in an area of the Liaoning province in Inner Mongolia (Hongshan culture 4700–2200 BC). Jade was used to create many utilitarian and ceremonial objects, ranging from indoor decorative items to jade burial suits. Jade was considered the "royal gem". 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.

Māori

In New Zealand, where it is known as greenstone, nephrite jade was fashioned for centuries by Māori to make weapons and ornaments, and is still widely used to make carved jewellery although the mining of it is restricted and closely monitored.

The Māori word for greenstone is pounamu. They call the South Island of New Zealand on the east side Te Wai Pounamu, meaning "The of Greenstone Water". Greenstone is highly valued by the Māori and it plays an important role in their culture. It is considered a taonga or treasure, and so is protected under the Treaty of Waitangi.

The Māori club, the mere, was often made of greenstone. Greenstone artefacts were often given as gifts to seal important agreements. Jewellery is still produced much of this is in traditional Māori designs.

Other names

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Besides the terms already mentioned, jadeite and nephrite are sometimes referred to by the following:

Jadeite

Agate verdâtre, Feitsui, Jadeit, Jadeita, Natronjadeit, Yunnan Jade, Yu-stone, Sinkiang jade

Nephrite

Aotea, Axe-stone, B.C. Jade, Beilstein, Grave Jade, Kidney Stone, Lapis Nephriticus, Nephrit, Nephrita, Nephrite (of Werner), New Zealand Greenstone, New Zealand Jade, Spinach Jade, Talcum Nephriticus, Tomb Jade

Faux Jade

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Many minerals are sold as jade. Some of these are: serpentine (also bowenite), carnelian, aventurine quartz, glass, grossularite, Vesuvianite, soapstone (and other steatites such as shoushan stone) and recently, Australian chrysoprase. "Korean jade," "Suzhou jade," "Styrian jade," "Canadian jade," "Olive jade" and "New jade" are all really serpentine; "Transvaal jade" is grossularite. Other names for faux jade are: "Honan jade," "Metajade" and "Xinjiang jade."

Jade may be enhanced (sometimes call "stabilized"). There are three main methods, sometimes referred to as the ABC Treatment System:

• Type A jadeite has not been treated in any way except surface waxing.
• Type B treatment involves exposing a promising but stained piece of jadeite to chemical bleaches and/or acids and impregnating it with a clear polymer resin. This results in a significant improvement of transparency and color of the material. Currently, infrared spectroscopy is the only test for the detection of polymer in jadeite.
• Type C jade has been artificially stained or dyed. 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.

Type A treatment is the only enhancement acceptable to professional collectors.

See also

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• Jade burial suit
• Jade (color)

Further reading

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• Laufer, Berthold, 1912, Jade: A Study in Chinese Archaeology & Religion, Reprint: Dover Publications, New York. 1974.
• Rawson, Jessica, 1975, Chinese Jade Throughtout the Ages, London: Albert Saifer, ISBN 0875567541

External links

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• Jade
• Jade: Chinese Stone of Heaven
• ancient chinese jade
• mindat.org
• Jade in Canada
• Chinese Jade

Silicate minerals | Gemstones

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