igneous
Olivine in Basalt (Peridot)
Magnesium Iron Silicate (Mg,Fe)2SiO4 (Mineral) within Basalt (Rock)
Hardness: 6.5–7 (Mohs); Color: Olive-green to lime-green; Luster: Vitreous to oily; Structure: Orthorhombic crystals, often granular or massive in basalt; Cleavage: Poor; Specific Gravity: 3.2–4.4.
- Hardness
- 6
- Color
- Olive-green to lime-green
- Luster
- Vitreous to oily
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Physical properties
Hardness: 6.5–7 (Mohs); Color: Olive-green to lime-green; Luster: Vitreous to oily; Structure: Orthorhombic crystals, often granular or massive in basalt; Cleavage: Poor; Specific Gravity: 3.2–4.4.
Formation & geological history
Formed deep within the Earth's upper mantle and brought to the surface by volcanic activity. Olivine is the first mineral to crystallize from a cooling mafic magma. Most specimens are relatively 'young' geologically (Cenozoic) though the mineral itself has existed since Earth's early crust formation.
Uses & applications
Used primarily as the gemstone Peridot when gem-quality; industrial uses include blast furnace refractory sand, casting molds, and as an abrasive in sandblasting.
Geological facts
Olivine is a major component of the Earth's upper mantle and has been found in meteorites (Pallasites) and on the surface of Mars and the Moon. It is often referred to as the 'Evening Emerald' due to its vibrant green glow under lamp light.
Field identification & locations
Identify in the field by its distinctive 'olive-green' sugary/glassy texture appearing as inclusions or nodules within dark, fine-grained volcanic rock like basalt. Common in volcanic regions such as Hawaii, Arizona (San Carlos), and the Canary Islands.
