... SiO2, Al2O3, K2O, Na2O and CaO, etc.. Feldspar group minerals in the earth's crust, the most widely distributed, ... crust. They are a common rock-forming minerals, which 60% Fu existence of magma, 30% distribution in the metamorphic rocks ... rocks, but only in a considerable enrichment of feldspar possible as industrial minerals. Feldspar group of four categories: Potash feldspar, albite, anorthite, ...