igneous
Basalt River Pebble
Aphanitic mafic volcanic rock
Hardness: 6-7 (Mohs); Color: Dark grey to black or dark greenish-brown; Luster: Dull to sub-vitreous; Crystal structure: Fine-grained/aphanitic; Specific gravity: 2.8-3.0
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey to black or dark greenish-brown
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey to black or dark greenish-brown; Luster: Dull to sub-vitreous; Crystal structure: Fine-grained/aphanitic; Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the surface of a terrestrial planet or moon. This specific specimen has been smoothed by fluvial erosion in a river or coastal environment over thousands of years.
Uses & applications
Commonly used in construction (crushed stone), decorative landscaping, 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 on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (high density), dark color, and lack of visible large crystals. Commonly found in riverbeds or on beaches near volcanic regions.
