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Carbonatite

Carbonatite is an igneous rock with a Mohs hardness of about 3–4 and a sugary to earthy luster, usually white, gray, brown or yellow.

An igneous rock made mostly of carbonate minerals. It fizzes like limestone, but it crystallized from magma.

Carbonatite specimen
Photo: Eurico Zimbres Zimbres, CC BY-SA 3.0, via Wikimedia Commons

How to identify carbonatite

  • Pale, and it fizzes in acid.
  • A knife scratches it.
  • Often with magnetite, mica or rare-earth minerals, and without fossils.

Often confused with

Where it's found

  • Ol Doinyo Lengai, Tanzania
  • Mountain Pass, California
  • Phalaborwa, South Africa
  • Fen Complex, Norway
  • Oka, Quebec

Uses

Rare-earth and phosphate ores, including Mountain Pass.

Rock tumbling

Not suitable for tumbling. Soft, and it fizzes.

Did you know?

Tanzania's Ol Doinyo Lengai is the only volcano erupting carbonatite lava today. The lava is black when molten and turns white as it weathers.

Carbonatite FAQ

What is carbonatite?

Carbonatite is an igneous rock with a Mohs hardness of about 3–4 and a sugary to earthy luster, usually white, gray, brown or yellow. An igneous rock made mostly of carbonate minerals. It fizzes like limestone, but it crystallized from magma.

How do you identify carbonatite?

Pale, and it fizzes in acid. A knife scratches it. Often with magnetite, mica or rare-earth minerals, and without fossils.

How hard is carbonatite?

Carbonatite has a Mohs hardness of about 3–4. A steel knife scratches Carbonatite, but a fingernail doesn't.

Where is carbonatite found?

Notable localities include Ol Doinyo Lengai, Tanzania; Mountain Pass, California; Phalaborwa, South Africa; Fen Complex, Norway; and Oka, Quebec.

What is carbonatite used for?

Rare-earth and phosphate ores, including Mountain Pass.

Can you tumble carbonatite?

It isn't a good choice for a rock tumbler. Soft, and it fizzes.

What is carbonatite often confused with?

Carbonatite is most often confused with Limestone, Marble and Calcite. Limestone is sedimentary and often has fossils; carbonatite is igneous. Marble is metamorphosed limestone and is usually not full of rare-earth minerals. Calcite is the mineral; carbonatite is the rock, a mix of carbonates.

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