Feldspar
Feldspars are a group of rockforming aluminium tectosilie minerals, containing sodium, calcium, potassium or barium. The most common members of the feldspar group are the plagioclase (sodiumcalcium) feldspars and the alkali (potassiumsodium) feldspars. Feldspars make up about 60% of the Earth's crust, and 41% of the Earth's continental crust by weight.