Magnesite

Magnesium carbonate, usually as white porcelain-like masses with a cauliflower texture.

Magnesite specimen — Photo: Robert M. Lavinsky, CC BY-SA 3.0, via Wikimedia Commons

How to identify magnesite

Chalky to porcelain-white, often knobbly.
Fizzes only in warm acid or as powder.
Harder than calcite.

Often confused with

Howlite
Howlite has gray web-like veins and doesn't fizz.
Compare side by side
Calcite
Calcite fizzes readily in cold acid.
Compare side by side

Where it's found

Liaoning, China
Austria
Bahia, Brazil
Nevada

Uses

Refractory bricks and magnesium metal.

Rock tumbling

Can be tumbled with care.

Did you know?

Porous magnesite is often dyed blue to imitate turquoise.

Think you could spot it from a blurry close-up?

Play today's Rocksday