Feldspar

Encyclopedy Index Feldspar is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earth's crust. Feldspars crystallize from magma in both intrusive and extrusive rocks; they occur as compact minerals, as veins, and are also present in many types of metamorphic rock. Rock formed entirely of plagioclase feldspar (see below) is known as anorthosite. Feldspars are also found in many types of sedimentary rock.

Feldspar is derived from the German Feld, field, and Spat, a rock that does not contain ore. Feldspathic refers to materials that contain feldspar. The alternative spelling, felspar, has now largely fallen out of use

This group of minerals consists of framework or tectosilicates:

· orthoclase a potassium-aluminium silicate,
· microcline also a potassium-aluminium silicate, and
· plagioclase a sodium-aluminium silicate to a calcium-aluminium silicate isomorphous series:

    · albite
    · oligoclase
    · andesine
    · labradorite
    · bytownite
    · anorthite

Uses

· Feldspar is a common raw material in the production of ceramics.
· Feldspars are used for thermoluminescence dating and optical dating in earth sciences and archaeology
· Feldspar is an ingredient in Bon Ami brand household cleaner.
· It is used as a glazing material

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