Anorthite
Anorthite is a silicate mineral prized by collectors for its exceptional color range, with known Chinese sources.
About Anorthiteextended article
Anorthite is the calcium-rich end-member of the plagioclase feldspar series, a calcium aluminium silicate. It sits at the opposite end of the series from sodium-rich albite, with intermediate compositions such as labradorite grading between them.
Properties
Anorthite is triclinic with two good cleavages meeting near 90 degrees, a hardness of 6–6.5 and frequent fine polysynthetic twinning seen as parallel striations on cleavage faces. It is usually white, grey or colourless with a vitreous lustre.
Occurrence
It is a high-temperature feldspar, characteristic of calcium-rich igneous rocks such as anorthosites and many basalts, of contact-metamorphosed limestones, and of meteorites and lunar highland rocks. It is a rock-forming member of the feldspar group.
About Anorthite
Anorthite belongs to the silicate class in the feldspar group / plagioclase series (ca end-member) and has the chemical formula CaAl2Si2O8. It crystallizes in the triclinic system and is one of the most visually varied minerals in the collector market.
Identification & care
Anorthite typically forms tabular crystals; commonly granular or massive in rocks. Its color range is broad, including white, gray, colorless, pale pink, and greenish. The luster is vitreous, pearly on cleavage, the streak is white, and specimens range from transparent to translucent. The cleavage is perfect {001}, good {010} — intersect at ~86° (triclinic, not 90°). The fracture is conchoidal to uneven, which aids identification.
Collector context
Collector notes
Anorthite holds a steady place in systematic mineral collections. Anorthite is widely represented across Chinese provinces, including Fujian, Gansu, Anhui, Guangdong.
Frequently asked questions
What is Anorthite?
Anorthite is a silicate mineral prized by collectors for its exceptional color range, with known Chinese sources.
What is the chemical formula of Anorthite?
The chemical formula of Anorthite is CaAl2Si2O8.
What crystal system does Anorthite belong to?
Anorthite crystallises in the Triclinic crystal system.
References & databases
Mindat.org is the world’s largest open mineralogy database. Our descriptions are written independently and fact-checked.