igneous
Spinifex Textured Komatiite
Ultramafic Komatiite (with Olivine Spinifex)
Hardness: 6-7 (Mohs scale); Color: Dark grey to greenish-black; Luster: Dull to vitreous; Crystal structure: Contains distinctive long, needle-like or blade-like crystals of olivine or pyroxene arranged in a criss-cross pattern; Specific Gravity: 3.0-3.4
- Hardness
- 6-7 (Mohs scale)
- Color
- Dark grey to greenish-black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Dark grey to greenish-black; Luster: Dull to vitreous; Crystal structure: Contains distinctive long, needle-like or blade-like crystals of olivine or pyroxene arranged in a criss-cross pattern; Specific Gravity: 3.0-3.4
Formation & geological history
Formed from extremely high-temperature (over 1600°C) lava flows with low viscosity, primarily during the Archean Eon (over 2.5 billion years ago). The spinifex texture results from rapid cooling and crystallization of olivine at the top of lava flows.
Uses & applications
Primarily used for geological research to understand the Earth's early mantle. They are also vital economic indicators as they often host major nickel-copper-platinum group element (PGE) sulfide deposits.
Geological facts
Named after the Australian 'spinifex' grass because the crystal patterns resemble the grass's spiky blades. Komatiites are rare because the Earth's mantle has cooled significantly since the Archean, making these types of volcanic eruptions nearly impossible today.
Field identification & locations
Identify by the unique 'matchstick' or criss-cross bladed pattern on the weathered surface. Commonly found in ancient 'greenstone belts' such as the Barberton belt in South Africa, the Abitibi belt in Canada, and the Yilgarn Craton in Western Australia.
