igneous
Basalt River Stone
Aphanitic Mafic Igneous Rock
Hardness: 5-6 Mohs. Color: dark gray to greenish-black. Luster: dull/matte. Texture: fine-grained (aphanitic). Structure: water-worn, sub-rounded to sub-angular. Specific gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- dark gray to greenish-black
- Luster
- dull/matte
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Physical properties
Hardness: 5-6 Mohs. Color: dark gray to greenish-black. Luster: dull/matte. Texture: fine-grained (aphanitic). Structure: water-worn, sub-rounded to sub-angular. 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. This specific specimen has been further shaped by fluvial erosion in a river or stream environment.
Uses & applications
Commonly used in construction (crushed stone), as architectural veneer, in hot stone massage therapies, and for landscaping.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its characteristic dark color, heavy weight for its size, and lack of visible large crystals. Common in volcanic regions and riverbeds downstream from volcanic plateaus.
