igneous
Basalt
Basalt (Mafic Volcanic Rock)
Hardness: 6; Color: Dark grey to black, weathering to brown; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic) or vesicular; SG: 2.8-3.1
- Hardness
- 6
- Color
- Dark grey to black, weathering to brown
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6; Color: Dark grey to black, weathering to brown; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic) or vesicular; SG: 2.8-3.1
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and floor tiles. High-quality basalt is used in the manufacture of stone wool as an insulator.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of large visible crystals. Look for small pin-holes (vesicles) or a fine-grained 'sugary' texture.
