Jade is an ornamental mineral, mostly known for its green varieties, which is featured prominently in ancient Asian art. The term jade is applied to two different minerals: Nephrite consists of a microcrystalline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (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 form of asbestos). The higher the iron content, the greener the colour. Jadeite is a sodium- and aluminium-rich pyroxene. The precious form of jadeite jade is a microcrystalline interlocking growth of jadeite crystals.