Jade is an ornamental stone. The term jade is applied to two distinct metamorphic rocks composed of different silicate minerals: Nephrite consists of a network of interlocking microcrystalline fibers of calcium, amphibole-rich (calcium-magnesium) ferroactinolite (calcium-magnesium-iron). The middle member of this series, with an intermediate composition, is called actinolite (the silky, fibrous mineral form is one of the forms of asbestos). The upper member is greener due to its iron content. Jadeite is a pyroxene rich in aluminum and sodium. The mineral used as a gemstone is the microcrystalline form of the matrix of interlocking crystals.