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Jade, Jadeite and Nephrite
Jade is one of the oldest gemstones known, with a history stretching back more than 7,000 years. But it was only in 1863 that gemologists discovered that jade is in fact two separate and quite distinct minerals: nephrite and jadeite. Though it can be difficult to tell them apart just by looking, the two varieties differ both in chemical composition and crystal structure. Experts can often detect nephrite by its lower translucency and luster. Nephrite tends to have a resinous luster, while jadeite is more vitreous.
Nephrite is by far the more common form of jade. Nephrite ranges in color from mid to dark green or grey-green, but it can also be white, yellowish or reddish. Nephrite is slightly softer than jadeite -- nephrite is 6 to 6.5 on the Mohs scale, while jadeite is 6.5 to 7. They have quite different chemical compositions as well: nephrite is a calcium magnesium iron silicate while jadeite is a sodium aluminum silicate. As a result, the two minerals also have different densities. Jadeite has a density of 3.30-3.38 while nephrite is less dense at 2.90-3.03.
|Chinese Nephrite Jade Carving|
The two varieties of jade also have different crystal structures. While jadeite's structure is an arrangement of grainy crystals, nephrite is made up of fibrous crystals that interlock in a matted texture. These densely packed and interwoven fibers are extremely resistant to fracturing. So while jadeite is the denser and harder jade, nephrite is actually the tougher of the two.
|Imperial Jade Burma|
All of the traditional Chinese jade is nephrite, since there are large deposits of nephrite in China, but no jadeite. Jadeite first came to China from Burma in the 18th century. Before the introduction of jadeite, the Chinese tended to value translucent white nephrite. But the jadeite from Burma came in a wider range of colors, including green, lavender, yellow, black and white.
The rarest and most valuable jadeite is called imperial jade, colored by traces of chromium. It has color and transparency rivaling fine emerald, though imperial jade is slightly more yellow in tone than emerald. You will also hear the term Type A used to refer to jadeite. Type A jadeite is untreated natural Burmese jadeite where the color is 100% natural.
The principal jadeite deposits are found in upper Burma (Myanmar). There are also deposits in other countries, including Russia, Canada, Japan and the USA. Nephrite deposits are found in China, Burma, New Zealand, Australia, Brazil, Canada, Zimbabwe, Russia and the USA.
See our selection of Fine Jadeite