igneous
Basalt River Stone
Aphanitic Mafic Igneous Rock
Hardness: 5-6 (Mohs); Color: Black to dark grey; Luster: Dull to sub-metallic; Crystal Structure: Fine-grained (aphanitic); Specific Gravity: 2.8-3.0. This specimen shows a smooth, water-worn texture.
- Hardness
- 5-6 (Mohs)
- Color
- Black to dark grey
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 5-6 (Mohs); Color: Black to dark grey; Luster: Dull to sub-metallic; Crystal Structure: Fine-grained (aphanitic); Specific Gravity: 2.8-3.0. This specimen shows a smooth, water-worn texture.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. These specific rounded shapes are formed through fluvial erosion in riverbeds or coastal wave action.
Uses & applications
Commonly used as decorative landscaping stones, massage stones (hot stones), in construction as aggregate, and occasionally in aquariums.
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
Identified by its dark color, heavy weight for its size, and lack of visible crystals. It is frequently found along riverbanks, beaches, and volcanic regions.
