igneous
Basalt River Stone
Basalt (Mafic volcanic rock)
Hardness: 5-6 (Mohs); Color: Dark gray to black with lighter phenocrysts; Luster: Dull to sub-metallic when wet; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark gray to black with lighter phenocrysts
- Luster
- Dull to sub-metallic when wet
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark gray to black with lighter phenocrysts; Luster: Dull to sub-metallic when wet; Structure: Fine-grained/aphanitic; 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 specimen shows significant rounding and smoothing due to fluvial (river) or glacial transport.
Uses & applications
Used in construction as crushed stone, for hot stone massage, in aquascaping, and as industrial cast basalt for wear-resistance.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible large crystals. Commonly found in volcanic regions, riverbeds, and coastal areas.
