Jade
Two tough minerals sold as one gem — jadeite and nephrite — revered above all in China.
Also known as: Jadeite, Nephrite
advanced Metamorphic subduction-zone rocks
What it is
"Jade" covers two distinct minerals with a similar look and cultural role: jadeite, a sodium aluminium pyroxene, and nephrite, a calcium magnesium amphibole. Both are only moderately hard — about 6 to 7 on the Mohs scale for jadeite and 6 to 6.5 for nephrite — yet exceptionally tough because of their interlocking fibrous structure, which let ancient cultures carve intricate objects that resist breaking.
Jadeite is the rarer and more valuable, with translucent emerald-green "imperial" jade the most prized; Myanmar is its principal source. Nephrite ranges from creamy white to spinach green and has a long history in China, New Zealand (as pounamu) and elsewhere. Dyeing and polymer impregnation are common treatments and should be disclosed.