igneous
Basalt River Stone
Basalt (Mafic volcanic rock)
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0. This specimen is water-worn and smooth.
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0. This specimen is water-worn and smooth.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specific specimen has been rounded and polished by hydraulic action in a river or coastal environment.
Uses & applications
Utilized in construction as aggregate, for paving, in 'hot stone' massage therapy, as aquarium decor, and in landscaping.
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 high density, dark color, and lack of visible crystals to the naked eye. River-worn specimens are found in any drainage basin cutting through volcanic terrain.
