26 June 2012

Classifications of Jadeite

The classification of Jadeite jade depends on the type of minerals present like astridite, eckermannite, kosmochlor and chromite. Sometimes you may also find other minerals such as albite, tremolite and diopside. However, the stone must have at least 75 percent of jadeite pyroxene to be called Jadeite jade.

With the growing demand for Jadeite jade especially the vivid green ones, many traders have resorted to treatment of Jadeite jade. Treated Jadeite jade is artificially coloured natural Jadeite Jade to improve their marketability and price. In gemmological practice, Jadeite jade is classified dependant on the type of treatments done on the stone.

Type A Natural Jadeite jade with no heating or chemical treatment.
Type B Jadeite jade is soaked in hydrochloric acid for several days to weeks to remove any impurities. Low heat is also applied to intensify the corrosion process. It is subsequently soaked in an alkali solution to loosen the grain before strengthening it with polymer material.
Type C Coarse grain Jadeite jade that has been coloured with dye using near colourless or Pale coloured Jadeite jade. The Jadeite jade has to be cleaned and heated to expand the grain boundaries before inducing the dyeing compound under vacuum to allow easier flow of the dye into the Jadeite jade. The most important factor in the dyeing procedure is the mixture for the dye solution so that the colours will turn out to be vivid and natural. There are several types of colouring solution: alcohol based, water based and oil based. The Jadeite jade is soaked in the solution and covered to prevent for evaporation. The soaking time depends on the varieties of the Jadeite jade and may take several days to a few weeks for the process.
Type B + C This process combines both Type B and Type C treatment process. The base material which lacks colour has to be dyed during a polymer impregnation process. The colour may be introduced separately or as a coloured polymer.
Coated Jade A green plastic film is skilfully applied to colourless, translucent Jadeite jade. It is so fine and smooth and can hardly be detected by the naked eye. The interlocking granular texture can still be seen in these stones when examined with a spot flashlight.

Other example of treatment is the heat treatment. With heat treatment, the colours of the Jadeite jade can be more pleasing. Acetic acid or bleach is used to clean away oil stains before heating. The heat treatment can be carried out in a stove with temperatures from 100 to 200 degrees Celsius. The heating process must be carefully carried out and should be stopped once the Jadeite jade turns red.

Evaluation of Jadeite jade can be easily remembered with 4Cs and 2Ts ; colour, clarity, carving, carat, texture and transparency. However, it is the colour that is the most important consideration. The colour consists of the hue, saturation, tone and distribution. Texture and transparency is also an important factor in quality evaluation. So before buying your Jadeite jade, you may want to get a Gemological assessment of you Jadeite jade today.

Recommended : Nanyang Gemological Institute, Singapore.

Read about Jadeite here.

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