igneous
Basalt River Stone
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6 (Mohs scale); Color: Dark grey to charcoal black; Luster: Matte (silky/glossy when wet); Crystal structure: Microcrystalline (Aphanitic); Specific gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to charcoal black
- Luster
- Matte (silky/glossy when wet)
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to charcoal black; Luster: Matte (silky/glossy when wet); Crystal structure: Microcrystalline (Aphanitic); Specific gravity: 2.8 - 3.0
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 and smoothed by fluvial erosion in a river or coastal environment.
Uses & applications
Used in construction as road base, concrete aggregate, and railroad ballast. Decorative uses include landscaping, massage stones, and aquarium decor.
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 heavy weight, dark color, and lack of visible crystals. Commonly found in riverbeds or beaches near volcanic regions.
