igneous
Basalt River Stone
Basalt (Mafic volcanic rock)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to slightly vitreous when wet or polished; Crystal structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to slightly vitreous when wet or polished
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to slightly vitreous when wet or 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 very near the Earth's surface. This specific specimen has been rounded and smoothed by water erosion in a river or coastal environment.
Uses & applications
Commonly used as decorative landscaping stone, in hot stone massage therapy, as construction aggregate, and in high-strength concrete.
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 and Mars.
Field identification & locations
Identify by its heavy weight (density), dark color, and fine-grained texture. It often shows tiny pits (vesicles) if it was gas-rich during formation, though this river-worn piece is smooth.
