Nephrite is a variety of the calcium and magnesium-rich amphibole mineral actinolite (aggregates of which also make up one form of asbestos). The chemical formula for nephrite is Ca2(Mg, Fe)5Si8O22(OH)2. It is one of two different mineral species called jade. The other mineral species known as jade is jadeite, which is a variety of pyroxene. While nephrite jade possess mainly grays and greens (and occasionally yellows, browns or whites), jadeite jade, which is rarer, can also contain blacks, reds, pinks and violets. Nephrite jade is an ornamental stone, used in carvings, beads, or cabochon cut gemstones.
Nephrite can be found in a translucent white to very light yellow form which is known in China as mutton fat jade, in an opaque white to very light brown or gray which is known as chicken bone jade, as well as in a variety of green colors. Canada is the principal source of modern lapidary nephrite. Nephrite jade was used mostly in pre-1800 China as well as in New Zealand, the Pacific Coast and Atlantic Coasts of North America, Neolithic Europe, and southeast Asia.
The name nephrite is derived from lapis nephriticus, which in turn is derived from Greek λίθος νεφρίτίκος; νεφρός λίθος, which means 'kidney stone' and is the Latin and Greek version of the Spanish piedra de ijada (the origin of "jade" and "jadeite"). Accordingly, nephrite jade was once believed to be a cure for kidney stones.