Feldspars

Feldspars: a group of tectosilicates including Potassium Feldspar (KAlSi3O8, Orthoclase), Sodium Feldspar (NaAlSi3O8, Albite), and Calcium Feldspar (CaAl2Si2O8, Anorthite). The latter two are mutually soluble in nearly all proportions, forming the isomorphic series of Plagioclases: Albite, Oligoclase, Andesine, Labradorite, Bytownite, and Anorthite.

feldspato
(Photo: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0/Wikimedia Commons, License CC BY-SA 3.0)

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