igneous
Basalt
Basalt
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Dull or matte. Crystal structure: Aphanitic (fine-grained), often with microscopic crystals. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on Mohs scale
- Color
- Dark gray to black
- Luster
- Dull or matte
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Physical properties
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Dull or matte. Crystal structure: Aphanitic (fine-grained), often with microscopic crystals. 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 aggregate, road base, railroad ballast, and high-quality concrete. It is also used as dimension stone for building and in the manufacturing of stone wool insulation.
Geological facts
Basalt is the primary component of the oceanic crust. It also makes up most of the surface of the Moon and Mars. Famous basalt formations include the Giant's Causeway in Northern Ireland and the Devils Postpile in California.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and very fine crystalline texture. It is ubiquitous in volcanic regions and along oceanic islands like Hawaii.
