igneous
Peridotite (Olivine Rock)
Peridotite (composed largely of olivine, (Mg, Fe)2SiO4)
Hardness: 6.5-7 (Mohs scale); Color: Olive-green to dark green; Luster: Vitreous to dull; Crystal structure: Orthorhombic mineral grains; Cleavage: Poor; Specific gravity: 3.2-4.4
- Hardness
- 6
- Color
- Olive-green to dark green
- Luster
- Vitreous to dull
Identified More igneous →
Explore Peridotite (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 (Mohs scale); Color: Olive-green to dark green; Luster: Vitreous to dull; Crystal structure: Orthorhombic mineral grains; Cleavage: Poor; Specific gravity: 3.2-4.4
Formation & geological history
Ultramafic igneous rock formed deep in the Earth's mantle or through the crystallizing of magma in deep crustal intrusions. Most found at the surface were transported by tectonic movement or volcanic activity (xenoliths).
Uses & applications
Source of peridot gemstones, industrial refractory materials, and sometimes harvested for nickel or chromium ores.
Geological facts
Peridotite is the dominant rock type of the Earth's upper mantle. Gem-quality olivine found in these rocks is known as peridot, the birthstone for August.
Field identification & locations
Identified by its distinctive olive-green color and heavy weight. Look for granular texture in basaltic areas or mountain belts containing mantle fragments (ophiolites).
