igneous
Olivine in Basalt (Peridotite Xenolith)
Forsterite-rich Olivine (Mg2SiO4) in Aphanitic Basalt
Hardness: 6.5-7 (Olivine), 5-6 (Basalt matrix); Color: Olive-green to lime-green phenocrysts in a grey/brown weathered matrix; Luster: Vitreous (glassy) on crystals; Crystal Structure: Orthorhombic; Specific Gravity: ~3.3
- Hardness
- 6
- Luster
- Vitreous (glassy) on crystals
Identified More igneous →
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Physical properties
Hardness: 6.5-7 (Olivine), 5-6 (Basalt matrix); Color: Olive-green to lime-green phenocrysts in a grey/brown weathered matrix; Luster: Vitreous (glassy) on crystals; Crystal Structure: Orthorhombic; Specific Gravity: ~3.3
Formation & geological history
Formed deep within the Earth's upper mantle or in magnesium-rich magma chambers. These specimens often represent 'xenoliths' (foreign rocks) brought to the surface by rapid volcanic eruptions of basaltic lava. Geological age varies by locality but typically ranges from Cenozoic to recent volcanic activity.
Uses & applications
Primary source of the gemstone Peridot; used in industry for refractory sand and casting, and as a geological indicator of mantle processes.
Geological facts
Olivine is one of the first minerals to crystallize from a cooling magma. It is also found in stony-iron meteorites known as Pallasites, making it a mineral of extraterrestrial significance.
Field identification & locations
Identify by looking for glassy green 'pockets' or crystals embedded in a dark, fine-grained volcanic rock. Commonly found in volcanic fields such as those in Arizona (Peridot Mesa), Hawaii, and various locations in Norway and China.
