igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6.0; Color: Dark grey to black, weathering to brown; Luster: Dull to earthy; Structure: Fine-grained, aphanitic, often vesicular; SG: 2.8-3.0.
- Hardness
- 6
- Color
- Dark grey to black, weathering to brown
- Luster
- Dull to earthy
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Physical properties
Hardness: 6.0; Color: Dark grey to black, weathering to brown; Luster: Dull to earthy; Structure: Fine-grained, aphanitic, often vesicular; SG: 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 continental flood basalt provinces.
Uses & applications
Extensively used in construction as aggregate for roads, concrete, and railroad ballast. Also used as dimension stone and in the manufacture of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up most of the surface of the Moon and Mars.
Field identification & locations
Identified by its dark color, heavy weight (relative to size), and fine-grained texture. Found worldwide, particularly in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.
