igneous
Basalt
Basalt
Hardness: 6 (Mohs); Color: Dark grey to black, weathering to brown; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6 (Mohs)
- Color
- Dark grey to black, weathering to brown
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs); Color: Dark grey to black, 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. Common in oceanic crust and volcanic regions.
Uses & applications
Extensively used in construction for aggregate, road base, asphalt filler, and as a component in concrete. Some dense varieties are used for floor tiles and monuments.
Geological facts
Basalt is the most common rock type on Earth's surface, making up most of the ocean floor and significant portions of the Moon, Mars, and Venus.
Field identification & locations
Identified in the field by its dark color, heavy weight for its size, and lack of visible crystals. Commonly found in lava fields, oceanic islands, and mid-ocean ridges.
