igneous
Spinifex Textured Komatiite
Komatiite (Mg-rich ultramafic volcanic rock)
Hardness: 5.5-6.0; Color: Dark grey to greenish-black; Luster: Dull to vitreous; Texture: Spinifex (acicular or bladed crystals of olivine or pyroxene); Specific Gravity: 3.0-3.3
- Hardness
- 5
- Color
- Dark grey to greenish-black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 5.5-6.0; Color: Dark grey to greenish-black; Luster: Dull to vitreous; Texture: Spinifex (acicular or bladed crystals of olivine or pyroxene); Specific Gravity: 3.0-3.3
Formation & geological history
Formed from high-temperature volcanic eruptions during the Archean Eon (over 2.5 billion years ago) where extremely low-viscosity lava cooled rapidly near the surface, allowing for the growth of long, bladed crystals.
Uses & applications
Primarily of geological research value; komatiites are also host rocks for significant nickel-copper-platinum group element (PGE) sulfide deposits.
Geological facts
Named after the Komati River in South Africa, these rocks are almost exclusively found in Archean-aged greenstone belts. They required lava temperatures exceeding 1,600°C to flow, which is much hotter than modern lava.
Field identification & locations
Identify by looking for the 'criss-cross' or 'birds-nest' pattern of long, dark bladed crystals. Found in ancient shield regions like the Yilgarn Craton (Australia), Abitibi Greenstone Belt (Canada), and Barberton Greenstone Belt (South Africa).
