A-Z of Gemstones: J

Posted on the 30th November -0001

A-Z of Gemstones: J: Jade

JADE

Jade is a name that is used to describe two similar but different materials, jadeite and nephrite with the first being more valuable.

Jadeite comes in different tones of green, yellow, orange, red, brown, violet, grey, black and white. The most valuable jadeites are semi-transparent stones with a pure green colour known as “Imperial” jade. The colour is caused by the presence of chromium.

Nephrite comes in different tones of greyish green and its colour is less saturated than jadeite’s green.

Jadeite can be semitransparent to opaque while nephrite is usually translucent to opaque and they mostly cut into cabochons, beads or carved into decorative ornaments.

Both jadeite and nephrite have vitreous to greasy lustres; jadeite rates 6.5-7.0 on the Mohs scale while nephrite rates 6-6.5 making it suitable for jewellery but vulnerable to scratching. Although jadeite does not rate very high on the Mohs scale it is considered one of the toughest gemstones which makes it suitable for jewellery that can withstand knocks, such as solid jade bangles.

Main sources of jadeite are: Guatemala, Russia and California, U.S.A but the finest quality stones usually come from Myanmar.

Jadeite can be treated to improve its lustre or colour. The main treatments are wax coating, bleaching, wax or polymer impregnation and dyeing. Nephrite can also be coated or impregnated but in general it is less likely to be treated.

There are no known commercially available synthesised jadeites or nephrites.

Materials that are mostly used to imitate jadeite and nephrite are assembled stones consisting of different combinations of pale jadeite, coloured cement, glass and plastic.

One of the most expensive pieces of jadeite jewellery in the world is a Cartier necklace consisting of 27 vivid green jadeite beads graduating in size from 15.4 to 19.2mm. The necklace was sold in 2014 for more than $27,4 million.