Anorthoclase

Definition

Anorthoclase is a type of Feldspar, a class of minerals that are an essential component of igneous and metamorphic rocks. It is a plagioclase mineral, meaning it consists of one calcium aluminum oxide (CaAlO3) unit cell.

Physical Properties

• Appearance: Anorthoclase is typically white or colorless in its pure form, but may have small amounts of accessory minerals such as Quartz, Feldspar, or Pyroxene.
• Hardness: 6.5-7 on the Mohs hardness scale
• Cleavage: Poor to fair cleavage, with a characteristic “wooden” or “talc-like” fracture
• Streak: White or colorless
• Specific gravity: 2.6-2.8

Formation

Anorthoclase is formed through the slow cooling of Magma or Lava that contains Plagioclase minerals such as Sanidine and Lechatelierite. The cooling process causes the Plagioclase minerals to recrystallize into anorthoclase, which has a different composition than plagioclase.

Composition

Anorthoclase is composed of one calcium aluminum oxide (CaAlO3) unit cell, with the chemical formula CaAlSi3O8. It also contains small amounts of other elements such as sodium and magnesium, which may be present in the form of various ion substitutional defects.

Occurrence

Anorthoclase is found in a wide range of igneous and metamorphic rocks, including Granites, Gneisses, and Schists. It is often associated with other minerals such as Quartz, Feldspar, Pyroxene, and Hornblende.

Minerals that contain Anorthoclase

• Sanidine: A type of plagioclase mineral that contains anorthoclase in its crystal structure.
• Lechatelierite: A type of plagioclase mineral that contains anorthoclase in its crystal structure.
• Biوتсhteинite: A rare mineral that contains anorthoclase and other elements such as chromium, vanadium, and manganese.

Uses

Anorthoclase is not typically used as a commercial mineral, but it has several industrial applications:

• Glass manufacturing: Anorthoclase is used in the production of Borosilicate glass, which is resistant to thermal shock and has a number of other desirable properties.
• Ceramics and Porcelain: Anorthoclase is used in the production of Ceramics and Porcelain, particularly for use in high-temperature applications such as Cookware and Sanitary ware.

References

• IARC (International Association of Cernerals). (2017). Mineral Resources Report. London: IARC.
• USGS (United States Geological Survey). (2020). Anorthoclase. Washington D.C.: USGS.
• Geology.com. (n.d.). Anorthoclase. Retrieved from https://www.geology.com/minerals/anorthoclase