igneous
Basalt River Stone
Extrusive mafic igneous rock (Basalt)
Hardness: 6; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic); Specific Gravity: 2.8–3.0. This specimen is water-worn and smooth.
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic); Specific Gravity: 2.8–3.0. This specimen is water-worn and smooth.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the surface of a planet or moon. Its rounded shape indicates it was transported and eroded by water in a river or coastal environment.
Uses & applications
Used in construction (crushed stone), as a heat retainer in sauna stones or hot stone massage, and in landscaping or aquarium 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
Identified by its heavy weight (high density), dark color, and fine grain. Common in volcanic regions and riverbeds. Collectors look for smooth, symmetrical shapes or unique inclusions.
