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Feldspar

Feldspars are a very common and diverse collection of minerals. They can be divied into three main groups: the Alkali Feldspars, Plagioclase, and Celsian groups. The Alkali Feldspars have a basic formula of (K,Na)[AlSi3O8]. The Plagioclase Feldspars have a basic formula of Na[AlSi3O8]-Ca[Al2Si2O8]. Celsian Feldspar is Ba[Al2Si2O8]. Felspars that are a blend of both the alkali and plagioclase formulas are also common. The ternary solid solution within which all the Alkali and Plagioclase feldspars fit has as its apices Albite (Na[AlSi3O8]), Orthoclase (K[AlSi3O8]), and Anorthite (Ca[Al2Si2O8]). A particular feldspar can be characterized as Anx-Aby-Orz.

Feldspar