igneous
Basalt with Olivine (Peridot)
Basalt containing (Mg,Fe)2SiO4
Hardness: 6-7 (Olivine), 5.5-6 (Basalt). Color: Dark gray to black matrix with olive-green phenocrysts. Luster: Vitreous in crystals, dull in matrix. Crystal structure: Orthorhombic olivine.
- Hardness
- 6-7 (Olivine), 5
- Color
- Dark gray to black matrix with olive-green phenocrysts
- Luster
- Vitreous in crystals, dull in matrix
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Physical properties
Hardness: 6-7 (Olivine), 5.5-6 (Basalt). Color: Dark gray to black matrix with olive-green phenocrysts. Luster: Vitreous in crystals, dull in matrix. Crystal structure: Orthorhombic olivine.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. Common in oceanic crust and volcanic islands.
Uses & applications
Basalt is used in road base, railroad ballast, and concrete aggregate. Large olivine crystals (Peridot) are used in jewelry.
Geological facts
Olivine is one of the first minerals to crystallize from a cooling magma and is a major component of the Earth's upper mantle.
Field identification & locations
Check for small, glassy green grains embedded in a dense, dark, fine-grained rock. Often found in volcanic fields like those in Hawaii, Arizona, or Iceland.
