Mineral Guide · Mineral

Gibbsite

Gibbsite is an aluminium hydroxide mineral and one of the principal components of bauxite, often forming pale plates or earthy masses.

Interactive 3D structure

Crystal structure

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Mineral properties

Formula: Al(OH)₃
Class: Hydroxides
Crystal system: Monoclinic
Typical colours: green, colourless, white, grey
Lustre: Dull, Pearly
Hardness: 2.50-3.50
Specific gravity: 2.30-2.40
Crystal habit: Botryoidal, Massive, Platy
Origin: intense tropical weathering profiles, bauxite deposits and low-temperature alteration zones

What is Gibbsite?

Gibbsite is an aluminium hydroxide mineral and one of the principal components of bauxite, often forming pale plates or earthy masses.

Mineralogy and structure

Reference formula: Al(OH)₃. Gibbsite is a layered aluminium hydroxide. It is soft and commonly occurs in earthy or cryptocrystalline material rather than large display crystals. Gibbsite belongs to the hydroxides and has a monoclinic crystal system. Typical hardness is 2.5–3.5 on the Mohs scale and specific gravity is approximately 2.3–2.4.

Colour and appearance

Typical colours include white, colourless, green, grey. The usual platy, botryoidal, massive habit and pearly, dull lustre are useful descriptive features, but colour alone is not diagnostic.

Formation and localities

Gibbsite forms in or is associated with intense tropical weathering profiles, bauxite deposits and low-temperature alteration zones. Important documented localities include Brazil, Guinea, Jamaica, India, China, Australia and the United States.

Collecting and care

Soft and easily scratched; keep dry, clean and protected from abrasion.

Sources and editorial review

Reviewed by NotOnlyRocks Editorial Team

Last reviewed: 31 August 2026

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