Nephrite Jade Butterflies. 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.
Nephrite can be found in a creamy white form (known in China as “mutton fat” jade) as well as in a variety of light green colours. Reference: Wikipedia