Anorthite

Anorthite
Anorthite from Japan
General
Category	Feldspar mineral
Chemical formula	CaAl2Si2O8
Identification
Color	White, grayish, reddish
Crystal habit	Anhedral to subhedral granular
Crystal system	Triclinic
Twinning	Common
Cleavage	Perfect [001] good [010] poor [110]
Fracture	Uneven to concoidal
Tenacity	Brittle
Mohs scale hardness	6
Luster	Vitreous
Diaphaneity	Transparent to translucent
Specific gravity	2.72 - 2.75
Optical properties	Biaxial (-), 2V 78° to 83°
Refractive index	nα = 1.573 - 1.577 nβ = 1.580 - 1.585 nγ = 1.585 - 1.590
Birefringence	δ = 0.012 - 0.013
References

Anorthite