igneous
Basalt
Basalt (containing Pyroxene, Plagioclase feldspar, and Olivine)
Hardness: 6-7 Mohs; Color: dark grey to black; Luster: dull/submetallic; Crystal Structure: aphanitic (fine-grained); Cleavage: none; Specific Gravity: 2.8 - 3.0
- Hardness
- 6-7 Mohs
- Color
- dark grey to black
- Luster
- dull/submetallic
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Physical properties
Hardness: 6-7 Mohs; Color: dark grey to black; Luster: dull/submetallic; Crystal Structure: aphanitic (fine-grained); Cleavage: none; Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. Common in oceanic crust and volcanic islands.
Uses & applications
Used primarily in construction for road base, concrete aggregate, and railroad ballast. Also used as dimension stone and in high-tensile industrial fibers.
Geological facts
Basalt is the most common rock type in the Earth's crust and also covers large areas of Mars and the Moon (lunar maria).
Field identification & locations
Identify in the field by its dark color, high density, and fine-grained texture with occasional small green olivine crystals. Found globally in volcanic regions.
