Anorthite
Image: Shannon Heinle (CC0)
Mineral NameAnorthite
Chemical FormulaCaAl2Si2O8
Mohs Hardness6
Crystal Systemtriclinic
Lustervitreous
Streak Colorwhite
Cleavageperfect on {001} and {010}, good on {110}
Fractureuneven to conchoidal
Specific Gravity2.76
Colorswhite, gray, colorless, yellowish, reddish
Transparencytransparent to translucent
Type LocalityHokkaido, Japan (among others)
Mineral Groupsilicates (tectosilicates, feldspar group)
Usescollector's item, scientific research
Associated Mineralspyroxenes, olivine, magnetite, other plagioclase feldspars
Rarityuncommon
Description
This image displays a blocky, white to grayish specimen of Anorthite, showing some of its characteristic cleavage planes and a somewhat dull to vitreous luster.
Geological Context
Anorthite is a primary mineral in mafic and ultramafic igneous rocks like gabbro, basalt, and anorthosite, forming at high temperatures. It can also be found in some high-grade metamorphic rocks.
