igneous
Basalt Pebble
Basalt
Hardness: 6.0-7.0 (Mohs); Color: Dark grey to black; Luster: Dull or earthy when weathered; Texture: Fine-grained aphanitic; Cleavage: None; Specific Gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull or earthy when weathered
Identified More igneous →
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Physical properties
Hardness: 6.0-7.0 (Mohs); Color: Dark grey to black; Luster: Dull or earthy when weathered; Texture: Fine-grained aphanitic; Cleavage: None; 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 surface of Earth. This specific specimen has been Rounded by water erosion in a river or coastal environment.
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, railroad ballast, and sometimes in landscaping or as river stones for decoration.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible crystals. It is ubiquitous in volcanic regions and along shorelines where volcanic activity once occurred.
