Forsterite

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Forsterite
Forsterite (peridot) crystal captured in space by NASA's Stardust spacecraft. Image released by NASA on 20 February 2006 at the annual meeting of the American Association for the Advancement of Science.
General
Category	Mineral
Chemical formula	Magnesium silicate (Mg₂SiO₄)
Identification
Colour	Green to yellow
Crystal system	Orthorhombic
Cleavage	, - imperfect
Fracture	Conchoidal
Mohs Scale hardness	7
Luster	Vitreous
Refractive index	α = 1.635, β = 1.651, γ = 1.670
Specific gravity	3.222

Forsterite (Mg₂SiO₄) is the magnesium rich end-member of the olivine solid-solution series. Forsterite crystallizes in the orthorhombic system (space group Pbnm) with cell parameters a 4.75 Å, b 10.20 Å and c Å 5.98.

Forsterite is associated with igneous rocks and has also been found in some iron meteorites. In 2005 it was also found in cometary dust returned by the Stardust probe.

The gemstone variety of Forsterite is known as Peridot.

References

Deer, W. A., Howie, R. A., and Zussman, J. (1992). An introduction to the rock-forming minerals (2nd ed.). Harlow: Longman ISBN 0-582-30094-0

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