igneous
Peridotite (Dunite / Olivine Rock)
Peridotite (predominantly Olivine, (Mg,Fe)2SiO4)
Hardness: 6.5-7.0 on Mohs scale. Color: Dark greenish-brown, olive green to brownish-black. Luster: Vitreous to greasy. Texture: Coarse-grained phaneritic. Specific gravity: 3.2-3.4.
- Hardness
- 6
- Color
- Dark greenish-brown, olive green to brownish-black
- Luster
- Vitreous to greasy
Identified More igneous →
Explore Peridotite (Dunite / Olivine Rock) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7.0 on Mohs scale. Color: Dark greenish-brown, olive green to brownish-black. Luster: Vitreous to greasy. Texture: Coarse-grained phaneritic. Specific gravity: 3.2-3.4.
Formation & geological history
Formed in the Earth's mantle through the crystallization of ultramafic magma under high pressure and temperature. It is brought to the upper crust via deep tectonic activity or mantle xenoliths in basaltic lavas.
Uses & applications
Used as a major source of magnesium, chromium (chromite inclusions), and nickel ores. High-quality olivine crystals within peridotite are cut as the gemstone peridot.
Geological facts
Peridotite forms the vast majority of Earth's upper mantle down to a depth of about 400 kilometers. It is extremely rich in magnesium and iron.
Field identification & locations
Identified in the field by its high density, heavy feel, and distinctive yellowish-green to brownish olivine grains. Commonly found in ophiolite complexes, diamond-bearing kimberlite pipes, and layered ultramafic intrusions.
