Mineral Guide · Mineral

Magnesite

Magnesite is a magnesium carbonate mineral with trigonal structure, pale natural colours and an important role in carbonate rocks and alteration zones.

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Crystal structure

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Mineral properties

Formula: MgCO₃
Class: Carbonates
Crystal system: Trigonal
Typical colours: White, Grey, Pink
Lustre: Vitreous
Hardness: 3.50-4.50
Specific gravity: 2.98-3.02
Origin: Igneous and sedimentary rocks, metamorphism or alteration of serpentinite and peridotite, and less commonly evaporites, hydrothermal veins and carbonatites.

What is magnesite?

Magnesite is magnesium carbonate with the formula MgCO3. It is a valid carbonate mineral and a member of the calcite group. Natural magnesite may occur as compact masses, fine-grained aggregates or well-formed crystals.

Mineralogy and appearance

Magnesite crystallises in the trigonal system and has a Mohs hardness of about 3.5 to 4.5. It is commonly white, colourless, greyish, yellowish, brown, pink or lilac. The lustre is usually vitreous, while inclusions and iron-bearing zones can add warm colour and pattern.

Formation and localities

Magnesite forms in altered magnesium-rich rocks, ultramafic environments, veins and some sedimentary or evaporitic settings. Important occurrences are known from Austria, Brazil, Australia, Greece, Spain, Turkey, the United States and many other regions.

Use in collections and mosaic

Fine-grained magnesite can be polished and used for pale backgrounds, soft veining and contrast with darker stones. Its relatively low hardness means that finished pieces should be protected from abrasion and harsh cleaning.

Sources and editorial review

Reviewed by NotOnlyRocks Editorial Team

Last reviewed: 31 August 2026

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