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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.
Plagioclase, Labradorite
Orthoclase
Plagioclase,
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