Peridot

 
Color : Yellow-green, olive green, brownish
Color of streak: White

Mohs’ hardness : 7.5-8
Specific gravity : 3.27-3.37   
Cleavage : Imperfect 

Fracture: Brittle, small conchoidal 
Crystal system : Orthorhombic
Chemical composition : Magnesium iron silicate
Refractive index : 1.654 –1.690
Double refraction : +0.036
Flourescence : None


The name derives from Greek, but the meaning is uncertain. Perhaps it refers to the numerous crystal planes of the crystal. The name “chrysolite” (Greek – gold stone) was formerly applied not only to peridot but also to many similarly colored stones. The name commonly used in mineralogy is olivine (because of its green color).

It has a vitreous and greasy luster, and is not resistant to sulphuric acid. It tends to burst under great stress, therefore is sometimes metal-foiled. Dark stones can be lightened by burning. Rarities are peridot cat’s eye and star peridot.

Peridot was brought to Europe by the crusaders in the Middle Ages and was often used for ecclesiastical purposes. It was very popular during the baroque period. It is not greatly desired by the trade because of its lower hardness. Used in table and emerald cuts, sometimes as brilliant.