A brief description of the color types for Jadeite (Jade) used at AGL Thai Laboratory Gemology.
Jade is an ornamental rock. The term jade is applied to two different metamorphic rocks that are composed of different silicate minerals:
• Nephrite consists of a microcrystalline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content, the greener the colour.
• Jadeite is a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystalline interlocking crystal matrix.
Jade may be enhanced (sometimes called "stabilized"). Note that some merchants will refer to these as grades, but it is important to bear in mind that degree of enhancement is different from color and texture quality. In other words, Type A jadeite is not enhanced but can have poor color and texture. There are three main methods of enhancement, 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 most accurate test for the detection of polymer in jadeite.
• Type C jade has been artificially stained or dyed. The effects are somewhat uncontrollable and may result in a dull brown. In any case, translucency is usually lost.
• B+C jade is a combination of B and C: it has been both impregnated and artificially stained.
• Type D jade refers to a composite stone such as a doublet comprising a jade top with a plastic backing.