Mineral Guide · Rock
Komatiite is an exceptionally magnesium-rich volcanic rock, famous for spinifex textures and for recording some of the hottest lavas in Earth's early history.
Komatiite is an exceptionally magnesium-rich volcanic rock, famous for spinifex textures and for recording some of the hottest lavas in Earth's early history.
Reference formula: No single formula applies because this is a rock.. Komatiite is a rock with variable olivine, pyroxene, glass and alteration minerals, not a single formula or crystal lattice. Its diagnostic spinifex texture reflects rapid crystallisation from high-temperature magma. Komatiite is classified with a rock rather than one mineral class and has a not applicable to the rock as a whole crystal system. Typical hardness is 5–6 on the Mohs scale and specific gravity is approximately 2.8–3.3.
Typical colours include green, dark green, black, brown. The usual massive, spinifex-textured, brecciated habit and dull, vitreous, sub-metallic lustre help describe a specimen, but colour alone is not diagnostic.
Komatiite forms in or is associated with Archean and Proterozoic ultramafic volcanic flows and ancient greenstone belts. Important documented localities include South Africa, Western Australia, Canada, Zimbabwe and India.
Komatiite is a standout educational and collector rock because its texture looks almost engineered: blades and plates of olivine or pyroxene record an ancient lava flow cooling at extraordinary temperature. It brings deep time into a cabinet.
Protect delicate spinifex surfaces and avoid acid cleaning; keep the field locality and texture visible rather than over-polishing the specimen.
Reviewed by NotOnlyRocks Editorial Team
Last reviewed: 28 August 2026
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