Diatomite

Chalky white rock made of the glassy shells of microscopic algae called diatoms.

Diatomite specimen — Photo: James St. John, CC BY 2.0, via Wikimedia Commons

How to identify diatomite

White, chalky and extremely light.
Powders on your fingers.
Doesn't fizz in acid (unlike chalk).

Often confused with

Chalk
Chalk fizzes in acid and is heavier.
Compare side by side
Kaolinite
Kaolinite becomes plastic when wet.
Compare side by side

Where it's found

Lompoc, California
Nevada
Denmark
Germany

Uses

Filters, pest control, abrasives and absorbents.

Rock tumbling

Not suitable for tumbling.

Did you know?

Alfred Nobel made dynamite by soaking nitroglycerin into diatomite.

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