Fayalite

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

Physical Properties
Chemical formula Fe2SiO4
Class Nesosilicate
Isolated tetrahedra
Crystal system Orthorhombic
Habit Granular
Prisms
Dipyramids
TabularCrystals large enough to display a
distinct habit are rare. Fayalite is
more commonly found as small,
rounded or embedded grains.
Color Green to yellow
Hardness 6.5
Specific gravity 4.4
Cleavage Poor (010) and (100)
Fracture Conchoidal
Luster Vitreous
Transparency Transparent to translucent
Streak White-yellow
Optical Properties
PPL High relief
Fractured appearance
Pale yellow or green
May be weakly pleochroic
XPL High relief
High 3rd order colorsFractures and high birefringence
combine to make a “stained glass”
appearance
δ 0.053
after Perkins, 341-342