igneous
Peridotite
Peridotite (Ultramafic Rock)
Hardness: 6.5 to 7; Color: Olive-green, dark green to yellowish; Luster: Vitreous to dull; Crystal structure: Orthorhombic (olivine); Specific gravity: 3.2 to 3.4. Highly dense and granular texture.
- Hardness
- 6
- Color
- Olive-green, dark green to yellowish
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5 to 7; Color: Olive-green, dark green to yellowish; Luster: Vitreous to dull; Crystal structure: Orthorhombic (olivine); Specific gravity: 3.2 to 3.4. Highly dense and granular texture.
Formation & geological history
Formed in the Earth's mantle through the slow cooling of ultramafic magma. It is the dominant rock of the upper mantle and is often brought to the surface through volcanic pipes or tectonic uplift.
Uses & applications
Primary source of chromium ore (chromite) and the gemstone peridot. Also used in carbon sequestration research due to its ability to react with CO2.
Geological facts
Peridotite makes up a large portion of the Earth's mantle. When it contains a high concentration of the mineral olivine, it can produce the August birthstone, peridot.
Field identification & locations
Identify by its characteristic olive-green color and high density. Look for it in ophiolite complexes or as xenoliths inside basaltic lava flows. It often weathers to a reddish-brown color on the surface.
