igneous
Basalt
Basalt
Hardness: 6.0; Color: Dark grey to black, often weathering to brown; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained) to porphyritic; Specific Gravity: 2.8–3.0
- Hardness
- 6
- Color
- Dark grey to black, often weathering to brown
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black, often weathering to brown; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained) to porphyritic; Specific Gravity: 2.8–3.0
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. It is the most common rock in Earth's crust (oceanic crust).
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality asphalt. It is also used as a dimension stone for floor tiles and monuments.
Geological facts
Basalt makes up most of the ocean floors on Earth. It is also widespread on the Moon and Mars. Many famous formations like the Giant's Causeway in Ireland are made of columnar basalt.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture. It often features small holes called vesicles. Commonly found in volcanic regions and coastal areas.
