igneous
Basalt River Pebble
Basalt
Hardness: 6-7 (Mohs scale); Color: Dark gray to olive green or black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: 2.8-3.0
- Hardness
- 6-7 (Mohs scale)
- Color
- Dark gray to olive green or black
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Dark gray to olive green or black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None; 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 specific specimen has been smoothed and rounded by river erosion/transportation.
Uses & applications
Commonly used in construction aggregate, road base, and decorative landscaping. Polished versions are used in massage therapy (hot stones) and fish tanks.
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 crystals. Commonly found in riverbeds, volcanic regions, and coastal areas.
