igneous
Basalt River Stone
Basalt (Mafic volcanic rock)
Hardness: 6-7 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy (especially when weathered); Crystal structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull/earthy (especially when weathered)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy (especially when weathered); 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. This specific specimen shows rounding and smoothing from fluvial erosion, likely in a river or stream bed.
Uses & applications
Commonly used as construction aggregate, road base, and in high-quality river stone landscaping or massage stones due to its heat retention properties.
Geological facts
Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. It is also found in abundance on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight for its size, and absence of visible crystals. It is ubiquitous in volcanic regions and riverbeds downstream from volcanic mountains.
