igneous
Basalt Pebble
Basalt (Mafic Volcanic Rock)
Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to sub-metallic when dry; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8–3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark gray to black
- Luster
- Dull to sub-metallic when dry
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to sub-metallic when dry; 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 near the Earth's surface. Often found in volcanic regions or transported to riverbeds and beaches by erosion.
Uses & applications
Used primarily in construction as aggregate for roads and concrete; occasionally polished for landscaping or massage stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It also exists on the Moon and Mars.
Field identification & locations
Identify by its dark color, fine grain, and heavy weight relative to its size. Often found as rounded pebbles in riverbeds or coastal areas.
