Diatomaceous earth ( /ˌdaɪ.ətəˌmeɪʃəs ˈɜrθ/) also known as D.E., diatomite, or kieselgur/kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. It has a particle size ranging from less than 3 micrometre to more than 1 millimeter, but typically 10 to 200 micrometres. This powder has an abrasive feel, similar to pumice powder, and is very light as a result of its high porosity. The typical chemical composition of oven-dried diatomaceous earth is 80 to 90% silica, with 2 to 4% alumina (attributed mostly to clay minerals) and 0.5 to 2% iron oxide.
Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, mild abrasive in products including toothpaste, mechanical insecticide, absorbent for liquids, matting agent for coatings, reinforcing filler in plastics and rubber, anti-block in plastic films, porous support for chemical catalysts, cat litter, activator in blood clotting studies, and a stabilizing component of dynamite. As it is heat-resistant, it can also be used as a thermal insulator.
Read more about Diatomaceous Earth: Specific Varieties, Climatologic Importance, Safety Considerations, The Age and Shape of Diatoms
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—Mark Twain [Samuel Langhorne Clemens] (1835–1910)