igneous
Basalt River Stone
Basalt (Mafic volcanic rock)
Hardness: 5-6 (Mohs); Color: Dark gray to black; Luster: Dull/Matte; Crystal Structure: Aphanitic (fine-grained); Texture: Smooth, water-worn pebble.
- Hardness
- 5-6 (Mohs)
- Color
- Dark gray to black
- Luster
- Dull/Matte
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark gray to black; Luster: Dull/Matte; Crystal Structure: Aphanitic (fine-grained); Texture: Smooth, water-worn pebble.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specific specimen has been rounded and smoothed by water erosion in a river or coastal environment.
Uses & applications
Commonly used as decorative landscaping stones, in construction (crushed stone), for hot stone massage therapy, and as aquarium substrate.
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 in the field by its dark color, heavy weight (high density), and lack of visible large crystals. Common in volcanic regions and riverbeds downstream from volcanic mountains.
