Pearls

Pearls have been highly valued as gemstones since antiquity, and their allure and beauty has always been magnified by the difficulty of obtaining them in early times. Unlike most other
gemstone which are minerals,Pearls are organic and are formed by living organisms. they are generally formed within the soft tissue layer of mollusks such as oysters and mussels. pearls are composed of calcium carbonate (in the form of Aragonate) and organic conchilin that build up as concentric layers as they are secreted by their host.

Chemical Formula: None

Color                    : White,Colorless,Blue,Red,Green,yellow,orange,brown,pink,purple,gray

Hardness              : 2.5-4.5

Crystal system      : Amorphous

Refractive index   : 1.52-1.69

SG                        : 2.6 - 2.8

Transparency        : Opaque

Double Refraction: .156

Luster                   :  Pearly

Cleavage              :  None

Mineral Class       :  Calcium carbonate and Conchiolin (organic) combined with water


Sources: 
            japan,Burma, china etc.