Diatomite
Diatomite, also called Diatomaceous Earth and Kieselguhr, a substance composed primarily of fossilized diatom shells. It occurs in large, hardened deposits. When ground into a powder, diatomite has a low density—about 10 pounds per cubic foot (160 kgm3). Powdered diatomite has exceptionally good filtering properties and is also highly absorbent, with the ability to absorb four times its own weight in liquids.
Nearly half of all diatomite produced commercially is used as a filtering medium, especially for swimming pools and public water supplies, and in the processing of raw sugar, vegetable oils, drugs, and beverages. Various manufacturing processes make use of diatomite's ability to absorb liquids. Another major use is as a filler in paints, asphalt, paper, and plastics. To prevent caking, diatomite is often added to detergents, fertilizers, and explosives. Diatomite's low density makes it very useful as heat insulation in boilers, industrial furnaces, and kilns.
Diatomite deposits occur in the United States (mainly in the western states) and in a few other countries. They were laid down under water in the Miocene Period more than 10,000,000 years ago. Submarine volcanic activity made the water rich in silica, which was absorbed by the diatoms and used in producing their glasslike shells.
Diatomite is chemically similar to the mineral opal, and has a general formula of SiO2H2O.