igneous
Basalt River Stone
Basalt
Hardness: 5-6 Mohs. Color: Dark grey to black. Luster: Dull to earthy. Crystal structure: Aphanitic (fine-grained). Specific gravity: 2.8-3.0. Texture: Smooth, water-worn.
- Hardness
- 5-6 Mohs
- Color
- Dark grey to black
- Luster
- Dull to earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs. Color: Dark grey to black. Luster: Dull to earthy. Crystal structure: Aphanitic (fine-grained). Specific gravity: 2.8-3.0. Texture: Smooth, water-worn.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specimen has been rounded and smoothed by water erosion in a river or coastal environment.
Uses & applications
Used in construction for road base and concrete aggregate. Smooth stones are popular in landscaping, aquarium decor, and hot stone massage therapy.
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 weight (denser than most light-colored stones), dark color, and fine grain. Found globally in volcanic regions and riverbeds.
