igneous
Olivine (Dunite)
(Mg,Fe)2SiO4 (Magnesium Iron Silicate)
Hardness: 6.5-7.0 (Mohs scale); Color: Olive-green to yellowish-green; Luster: Vitreous to dull when weathered; Crystal Structure: Orthorhombic; Specific Gravity: 3.2-4.4
- Hardness
- 6
- Color
- Olive-green to yellowish-green
- Luster
- Vitreous to dull when weathered
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Olive-green to yellowish-green; Luster: Vitreous to dull when weathered; Crystal Structure: Orthorhombic; Specific Gravity: 3.2-4.4
Formation & geological history
Formed in the Earth's upper mantle and brought to the surface via volcanic eruptions or tectonic uplift. Often found as xenoliths in basalt or as the primary component of the ultramafic rock Dunite.
Uses & applications
Primary source of magnesium; used as a flux in steel making, as refractory sand for casting, and as a gemstone (Peridot) when high quality.
Geological facts
Olivine is a major component of the Earth's upper mantle and has also been discovered on Mars and in lunar meteorites.
Field identification & locations
Identify by its distinctive olive-green color and 'sugary' granular texture. Commonly found in basalt fields, riverbeds draining volcanic areas, and green sand beaches like Papakōlea in Hawaii.
