Feldspar

Feldspar (KAlSi3O8-NaAlSi3O8-CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up as much as 60% of the Earth’s crust. Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks & are present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is called anorthosite. Feldspars are also found in many types of sedimentary rocks.