Diatomaceous earth (also known as DE, TSS, diatomite, diahydro, kieselguhr, kieselgur and celite) is a naturally occurring, soft, chalk-like sedimentary rock that is easily crumbled into a fine white to off-white powder. This powder has an abrasive feel, similar to pumice powder, and is very light, due to its high porosity. The typical chemical composition of diatomaceous earth is 86% silica, 5% sodium, 3% magnesium and 2% iron.
Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, as a mild abrasive, as a mechanical insecticide, as an absorbent for liquids, as cat litter, as an activator in blood clotting studies, and as a component of dynamite. As it is also heat-resistant, it can be used as a thermal insulator.
Because diatomite forms from the remains of water-borne diatoms, it is found close to either current or former bodies of water. It is generally divided into two categories based upon source: freshwater and saltwater. Freshwater diatomite is mined from dry lakebeds and is characteristically low in crystalline silica content. Saltwater diatomite contains a high crystalline silica content, making it a useful material for filters, due to the sieve-like features of the crystals.