igneous
Basalt River Stone
Basalt (Mafic volcanic rock)
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0; Contains plagioclase feldspar, pyroxene, and olivine.
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to earthy
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0; Contains plagioclase feldspar, pyroxene, and olivine.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specimen has been rounded by fluvial erosion in a river environment.
Uses & applications
Basalt is used in construction (crushed stone), as an industrial aggregate, and in landscaping. Smaller, smooth specimens are popular for decorative use and hot stone massage.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the ocean floors and the lunar maria on the Moon.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture. Commonly found in volcanic regions or in riverbeds downstream from volcanic sources.
