A great many industrial materials begin as non-metallic minerals. Lime (calcium oxide), a widely available material, is used in cement, building construction, agriculture, paper making, chemical manufacturing, and even iron and steel. Silica, composed of silicon and oxygen of several varying crystalline forms or polymorphs, is a primary source for glass, filtration systems, foundry castings, and metallurgical applications. Diatomite is a powdery mineral composed of the fossilized remains of microscopic single-celled aquatic plants called diatoms and is used for additives to paints and plastics, filtering agents, and absorbents to mitigate spills in the automotive, industrial, janitorial and waste remediation industries. The list of industrial minerals includes talc, bentonite, saprolite, borate, gypsum, kaolin, and feldspar, to name a few.