Feldspar

Feldspar is a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. They crystallize from magma in both intrusive and extrusive igneous rocks, as veins, and are also present in many types of metamorphic rock.

Composition

Feldspars are a group of closely related minerals that together are the most abundant mineral group on Earth. They have nearly identical crystal structures but varying chemical compositions. The general formula for the feldspar structure is X(Al,Si)4O8, where X can be Na, K, or a variety of Ca or Ba.

Types of Feldspar

There are several types of feldspar:

• Orthoclase (KAlSi3O8) - Orthoclase is a monoclinic system mineral, usually white or pink. Its name is derived from the Greek words for "straight fracture," because its two cleavage planes are at right angles to each other.
• Albite (NaAlSi3O8) - Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series.
• Anorthite (CaAl2Si2O8) - Anorthite is the calcium endmember of plagioclase feldspar. Anorthite is white, grayish, or reddish in color.

Uses

Feldspar is used in many industries, such as glassmaking, ceramics, and as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, and resistance to chemical corrosion.

See Also

• Mineral
• Rock (geology)
• Igneous rock
• Metamorphic rock

References

Feldspar Resources
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