When aquatic diatoms die they drop to the bottom, and the shells, not being subject to decay, collect in the ooze and eventually form the material known as diatomaceous earth (sometimes called kieselguhr). When it occurs in a more compact form as a soft, chalky, light-weight rock, it is called diatomite. Deposits of diatomaceous material, formed underwater in past geologic time and now exposed above water, are found in all parts of the world. Diatomite is much used as an insulating material against both heat and sound, in making dynamite and other explosives, and for filters, abrasives, and similar products. Most of the earth's limestone has been deposited by diatoms, and much petroleum is of diatom origin.
Diatoms are classified in the phylum (division) Chrysophyta , class Bacillariophyceae.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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