igneous
Basalt (or similar Mafic Igneous Rock)
Basalt
Hardness: 6-7 on Mohs scale. Color: Dark gray to black, often weathering to brown or reddish-brown. Luster: Dull to earthy. Crystal structure: Aphanitic (fine-grained), typically lacks visible crystals to the naked eye. Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Dark gray to black, often weathering to brown or reddish-brown. Luster: Dull to earthy. Crystal structure: Aphanitic (fine-grained), typically lacks visible crystals to the naked eye. 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 volcanic rock on Earth.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for paving or landscaping. Also used in high-temperature insulation (mineral wool).
Geological facts
Basalt underlies more of Earth's surface than any other rock type; most ocean basins are composed of basalt. It is also found extensively on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (density), dark color, and fine-grained texture. It often shows a weathered crust ('rind') that is lighter in color than the fresh interior. Commonly found in volcanic regions and riverbeds.
