Diatomite is a soft, chalk-like sedimentary rock composed of the fossilized remains of diatoms, which are microscopic aquatic algae. Diatoms have an elaborate internal silica skeleton and over 10,000 living and fossilized diatom species have been identified. Diatomite deposits form from the accumulation of the silica cell walls of diatoms and are commonly a light color like white or yellow. Diatomite has a variety of industrial uses and applications.