igneous
Basalt (River Pebble)
Mafic volcanic rock (rich in magnesium and iron)
Hardness: 6-7 on Mohs scale; Color: dark grey to black; Luster: dull to earthy; Texture: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0
- Hardness
- 6-7 on Mohs scale
- Color
- dark grey to black
- Luster
- dull to earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: dark grey to black; Luster: dull to earthy; Texture: Aphanitic (fine-grained); 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 Earth's surface. This specimen has been rounded by fluvial erosion in a river environment.
Uses & applications
Used as aggregate in construction, road base, decor, and river rock 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 on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (high density), dark color, and fine-grained texture. Commonly found in riverbeds, volcanic fields, and coastal areas.
