igneous
Basalt
Basalt
Hardness: 6 (Mohs scale); Color: Black to dark gray; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Cleavage: Poor; Specific gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Black to dark gray
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Black to dark gray; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Cleavage: Poor; 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 concrete. It can also be used as a dimension stone for floor tiles and monuments.
Geological facts
Basalt is the primary rock type making up the Earth's oceanic crust. It is also found on the Moon and Mars, where basaltic plains (Maria) are visible from Earth.
Field identification & locations
Identified in the field by its dark color, heavy weight (relative to volume), and fine-grained texture lacking visible crystals. Commonly found in volcanic regions and oceanic islands like Hawaii and Iceland.
