Peridot

Octagonal Peridot

General
Peridot is a bright yellow green or golden green variety of olivine. It was originally found on Egypt's St. John's Island once known as Topazios, in the Red Sea, which is now known as Zeberget. It is also found in Burma, Sri Lanka, USA and Norway.
Because there hardness is lower than 7, they are not ideal for use in rings, and should be treated with reasonable care.

Colour
Bright golden green, but can vary to darker green or greenish yellow. Peridot has also been known as Chrysolite, although this is an old name which was applied fairly indiscriminately to any yellow and greenish yellow stones. It was also once incorrectly called topaz. There are also brown peridots. Since1952 many stones believed to be brown peridots have been found to be a different mineral called Sinhalite.

Technical Information

Chemical Composition and Name	Magnesium Iron Silicate (MgFe)2SiO4*
Hardness	6.5 to 7
Refractive Index	1.650 - 1.688 to 1.668 - 1.706
Bi-refringence	0.038
Optic Sign	Positive
Optical Character	Biaxial
Specific Gravity	3.34

Notes
* The iron and magnesium are interchangeable, so that peridot can vary from Mg₂SiO₄ known as Forsterite, to Fe₂SiO₄ known as Fayalite.