Description

Feldspars (KAlSi3O8 NaAlSi3O8 CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up about *1% of the Earth\'s continental crust by weight.[2]
Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock.[3] Rock formed almost entirely of calcic plagioclase feldspar (see below) is known as anorthosite.[4] Feldspars are also found in many types of sedimentary rocks.