Mineral name: Feldspars are a group of minerals made of aluminum, silicon, and oxygen. Examples include orthoclase, plagioclase, labradorite, and microcline.
Chemical formula: KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8
Physical properties: vitreous luster, hardness 6, white streak, two directions of cleavage
Feldspars are used in glass making, so put a feldspar color dot on all the glass items that you marked for quartz.
Feldspars are also used in making ceramics, pottery, and fine china.
Feldspars are also ground to produce scouring powders and other cleaning products. The powder is hard enough to scrape away rust and stains, but soft enough not to scratch glass, steel, or porcelain.