igneous
Basalt
Basalt
Hardness: 5-6 Mohs. Color: dark grey to black. Luster: dull to velvety. Structure: fine-grained (aphanitic). Cleavage: none. SG: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- dark grey to black
- Luster
- dull to velvety
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Physical properties
Hardness: 5-6 Mohs. Color: dark grey to black. Luster: dull to velvety. Structure: fine-grained (aphanitic). Cleavage: none. SG: 2.8-3.0.
Formation & geological history
Extrusive volcanic rock formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the surface of a planet or moon.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and dimension stone for flooring or monuments.
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up most of the ocean floors. It is also found on the Moon and Mars.
Field identification & locations
Identified by its dark color, heavy weight for its size, and absence of large visible crystals. Found globally in volcanic fields and oceanic ridges.
