igneous
Basalt
Mafic Igneous Rock
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull/Submetallic when fresh; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull/Submetallic when fresh
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull/Submetallic when fresh; Crystal structure: Aphanitic (fine-grained); Cleavage: None; 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. Most common rock on Earth's crust.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for paving. Some varieties are used in mineral wool insulation.
Geological facts
Basalt is the primary rock of the ocean floor and covers most of the volcanic islands like Hawaii and Iceland. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture. Found near volcanic sites and oceanic crust outcrops.
