Jade

Jade is an ornamental stone. The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals:
 * Nephrite consists of a microcrystaline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middleJade.jpg 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 microcrystaline interlocking crystal matrix.

Source

 * http://en.wikipedia.org