How do I identify Anorthite?

Anorthite can be identified by its hardness of 6 - 6.5 on the Mohs scale, Colourless color. Look for these key characteristics when examining specimens.

What color is Anorthite?

Anorthite typically appears in Colourless, reddish grey, white. Color can vary depending on impurities and formation conditions.

How hard is Anorthite?

Anorthite has a hardness of 6 - 6.5 on the Mohs scale. This gives it moderate hardness.

Anorthite

A variety of Minerals

What is Anorthite?

Anorthite is the calcium endmember of the plagioclase feldspar mineral series. The chemical formula of pure anorthite is CaAl2Si2O8. Anorthite is found in mafic igneous rocks. Anorthite is rare on the Earth but abundant on the Moon.

Optical Properties

Refractive Index: 1.575-1.588
Birefringence: 0.013
Optical Character: Biaxial negative

Anorthite Market Value Calculator

Estimate the market value of Anorthite using size, quality, and finish. This preview calculator is for quick context and is not a formal appraisal.

Anorthite Localities Map

See where Anorthite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

Map preview

North ZoneCentral RidgeSouth Basin

Key Characteristics

Formation of Anorthite

Anorthite is a rare compositional variety of plagioclase. It occurs in mafic igneous rock. It also occurs in metamorphic rocks of granulite facies, in metamorphosed carbonate rocks, and corundum deposits. Its type localities are Monte Somma and Valle di Fassa, Italy. It was first described in 1823. It is more rare in surficial rocks than it normally would be due to its high weathering potential in the Goldich dissolution series. It also makes up much of the lunar highlands; the Genesis Rock is made of anorthosite, which is composed largely of anorthite. Anorthite was discovered in samples from comet Wild 2, and the mineral is an important constituent of Ca-Al-rich inclusions in rare varieties of chondritic meteorites.