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CC …Distinguishing Antique Jades

The jade collectors often say that they distinguish antique jades from modern or counterfeit ones by examining a piece in 4 aspects:

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[ A partial view of the celadon jade mountain carved by the court order of Emperor Qianlong of Qing Dynasty c. 1660]

Only if everything mentioned BELOW is in order, we will comfortably take the piece into our antique jade collection. If the test fails in a single aspect or if the collector has doubt in any aspect, it is advisable not to take the piece because a single mistake might cause substantial loss of money.

  1. Material – the material of the piece should only be nephrite unless it is a Qing piece when Jadeite started to play an important role as jade.
  2. Design – the design and form of the piece should be characteristic of the stated era. The form of a Song (A.D.960 – 1279) dragon carved on a jade piece is definitely different from that of a Qing (A.D.1644 – 1911) piece. While that carved on a Ming (A.D.1368 – 1644) piece might retain some characteristics of a Yuan (A.D.1279 – 1328) dragon and also have some characteristics of a Qing piece indicating the “evolution” of the design and the change in trend of the dragon form.
  3. Craftsmanship – the craftsmanship is “old”. The tool marks left on the surface of the pieces is consistent with those made by the manual carving treadle lathe and piercing by drilling or wire cutting. The essence of carving with these tools is by rubbing or grinding of metal disk, solid or hollow drill bits and metal wire with harder sand-like materials against the jade. The appearance of the bottom side of the carved lines should be grain-like as these lines are narrow and cannot be polished. The reticulated areas or holes that are rougher than the well- polished surface areas should show oxidation more seriously and obviously, and the patina and polishing is soft.
  4. Burial marks – the burial marks should be natural and not superficial if the jade piece had at least been once buried in a tomb. They had been subjected to corrosion and weathering for hundred of years when they were in the tomb in contact with a moist, alkaline or some unknown diverse environment. Some chemical or physical changes might have taken place within the jade.

So we now come to the discussion of nephrite jade.

As said last time, nephrite is basically some sort of mineral rock. Chemically it is a kind of crystallized fibrous calcium and magnesium silicate compound with interlocking structure believed to be formed under low pressure (below 2500 Bar) and low temperature (around 300 to 340 degree Celsius) during the mountain building period of the Earth. It is known as Tremolite in mineralogy with a chemical formula of Ca2Mg5 [ Si4O11]2[OH]2.

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[ A late Yuan Dynasty c. 1271–1368, spinach jade belt hook ]

Pure Tremolite is white in colour and extremely rare. In nature in Xinjiang province of China where nephrite jade has been mined for thousands of years and was before 1980’s the only place that nephrite was mined, it is often associated with various impurities like Actinolite and Ferro-actinolite adding on top of the white colour a greenish tint, or with graphite making it grey or black, and with chromium oxide giving it the green colour of the spinach nephrite jade.

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The so-called mutton-fat jade that is pure white has a Tremolite content of over 99%. Its existence is rare and up till now I have never seen a single piece. Normal white jade has over 95% Tremolite content. The infamous celadon jade mountain [first photo above] carved during the Qianlong period under the court order of Emperor Qianlong and now exhibiting in the Palace Museum of Beijing has a Tremolite content of 89% and 6% Actinolite. Grey or black nephrite has a graphite content of 5% to 20%. Spinach nephrite jade has Tremolite content between 75% to 90% and other impurities. Unlike spinach jade mined in Canada in recent years, those mined in Xinjiang have finer crystals and always have black impurities.

I shall talk about the physical properties of nephrite and touch on other nephrite jades mined in Qinghai province and in the Lake Baikal region of Russia since 1980’s later.

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One Comment

  1. Posted April 7, 2010 at 3:20 pm | Permalink

    Dear Susan

    Very nice, thanks.

    Have fun
    anita
    http://www.translucentworld.com/forum/phpBB3/index.php

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