Coal

A rock formed from buried, compressed plant material — ancient swamp forests turned to stone.

Coal specimen — Photo: Amcyrus2012, CC BY 4.0, via Wikimedia Commons

How to identify coal

Black and very light for a rock.
Leaves black dust on hands.
Layered, with blocky or curved breaks.
Burns.

Often confused with

Obsidian
Obsidian is glass: harder, heavier and translucent at the edges.
Compare side by side
Shale
Black shale is heavier and won't burn.
Compare side by side

Where it's found

Powder River Basin, Wyoming
Appalachia
Shanxi, China
Ruhr, Germany

Uses

Energy and steelmaking (as coke).

Rock tumbling

Not suitable for tumbling.

Did you know?

Jet, the black gem of Victorian mourning jewelry, is a variety of coal.

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