A diatom is an organism that is a member of the phylum of algae called Bacillariophyta. There are about 60,000 species of these algae presently known. Experts estimate that there are more likely 600,000 to 6,000,000 species in total!

Diatoms are single-celled (unicellular) organisms that live as individuals or in groups called colonies. They exist in all the waters of the Earth, both salt and fresh. They form shells made out of silica (the mineral name of this silica is opal) which they extract from the water. As can be seen in these pictures, their microscopic shells are very intricate and beautiful and have rightly been called "the jewels of the sea." Diatoms are very abundant and provide food for many aquatic animals.

When diatoms die, their silica shells accumulate on the floor of the body of water in which they lived. Thick layers of these diatom shells have been fossilized (that is, preserved) in the rock record. Such layers, or beds, of diatoms are called diatomaceous earth, or diatomite. Diatomaceous earth is white to cream color. It is very porous which makes it useful in a number of filtering applications.


The name diatom comes from a Greek word diatomos that means cut in half, because the shells of diatoms have two overlapping, symmetrical halves.


In the United States, large deposits of diatomite are found in California, Nevada, Washington and Oregon. Of these states, California and Nevada produce the largest amount of diatomite. Significant producers of diatomite worldwide include France, China, Denmark, Russia, and Algeria. Diatomite resources worldwide will meet demand for the foreseeable future. However, new deposits that can be economically mined need to be identified.

The United States produces much of its own diatomite material. Still, some is imported from France, Mexico, and other nations.


Because of its porosity, diatomite has been used extensively as a filter for a variety of purposes. It is used to filter impurities out of everything from beer and wine to oils and greases. Similarly, diatomite is used to filter impurities from water to produce drinkable (potable) water in public water systems. In this situation, the diatomite removes bacteria and protozoa.

The oldest use of diatomite is as a very mild abrasive and for this purpose has been used in toothpaste and metal polishes.

It is also used in paper, paint, brick, tile, ceramics, plastics, soaps, detergents and other products as a filler. A filler is a substance that increases the volume of a product and/or fills in space.

Diatomite has also found value as an insulating material in high-temperature mechanisms like furnaces and boilers. It has also proven effective as a sound insulator.

Substitutes and Alternative Sources

Diatomite is easily replaced by other materials for most of its applications. For example, silica sand and an expanded form of the material perlite can be used in filtration applications. Talc, ground lime, ground mica, and clay can be used as filler material. Despite these many options, its ready availability, abundance and low cost will guarantee its use for many decades to come.

(Information adapted from "Minerals in Your World", a cooperative effort betweeen the U.S. Geological Survey and the Mineral Information Institute.)

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