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Peridot

Gem-quality specimens of the mineral olivine are called peridot by gemmologists. Peridot has an olive- bottle-green colour due to the presence of iron, and a distinctive oily or greasy lustre. It has a high birefringence, so doubling of the back facets can easily been seen in larger specimens when viewed from the front. Good-quality crystals are very rare.

Occurrence

Peridot is found on St. John’s Island (Egypt), in Norway, Brazil, China, Burma, Hawaii and Arizona (USA), South Africa, and Australia.

Remark

The crusaders brought peridot to Europe in the Middle Ages, transporting stones from St. John’s Island in the Red Sea, where it has been mined for over 3,500 years.

Crystal structure	Orthorhombic
Composition	Magnesium iron silicate
Hardness	6.5
SG	3.34
Rl	1.64-1.69
DR	0.036
Lustre	Vitreous to greasy