igneous
Basalt River Stone
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to mildly sub-metallic when polished; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to mildly sub-metallic when polished
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to mildly sub-metallic when polished; 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. These specific specimens have been rounded by water erosion in a river or coastal environment.
Uses & applications
Commonly used for hot stone massage therapy, aquarium decor, landscaping, and as a raw material in construction (crushed stone).
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
Identified by its heavy weight relative to size and dark, uniform, fine-grained texture. Found globally in volcanic regions or riverbeds downstream from volcanic plateaus.
