igneous
Basalt
Basalt
Hardness: 5-6 (Mohs); Color: Dark grey to black, sometimes weathering to brown; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0.
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to black, sometimes weathering to brown
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to black, sometimes weathering to brown; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. It is a volcanic rock common in oceanic crust and volcanic islands.
Uses & applications
Extensively used in construction, road base, concrete aggregate, railroad ballast, and sometimes as a heat-retaining stone for therapy or sauna use.
Geological facts
Basalt is the most common rock type on Earth's crust and makes up most of the ocean floors. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its heavy weight (density), dark color, and fine-grained texture. It is often found in riverbeds as rounded pebbles or in large volcanic flows (columns).
