igneous
Basalt River Stone
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal black; Luster: Dull to sub-vitreous; Crystal Structure: Microcrystalline; Cleavage: None; Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to charcoal black
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal black; Luster: Dull to sub-vitreous; Crystal Structure: Microcrystalline; Cleavage: None; Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. This specific specimen has been further shaped and polished by fluvial (river) erosion over thousands of years.
Uses & applications
Commonly used in landscaping, decorative aquariums, massage therapy (hot stone massage), and as a basic construction aggregate.
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
Identify by its heavy weight relative to size (high density), dark matte color, and rounded shape if found near water. Extremely common globally, especially in volcanic regions.
