Forsterite

For gigapans and thin section images, please see the olivine page.

Physical Properties
Chemical formula Mg2SiO4
Class Nesosilicate
Isolated tetrahedra
Crystal system Orthorhombic
Habit Granular
Prisms
DipyramidsTabular

Crystals large enough to display a distinct
habit are rare. Forsterite is more commonly
found as small, rounded or embedded grains.

Color Green
Colorless
Hardness 6.5
Specific gravity 3.2
Cleavage Poor (010) and (100)
Fracture Conchoidal
Luster Vitreous
Transparency Transparent to translucent
Streak White
Optical Properties
PPL Colorless
High relief
Fractured appearance
XPL High relief
High 3rd order colors
Fractures and high birefringence combine
to make a “stained glass” appearance
δ 0.035
after Perkins, 340-341