igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness: 6 on Mohs scale; Color: Dark gray to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), microscopic crystals; Specific gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark gray to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), microscopic crystals; Specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the surface of a planet or moon.
Uses & applications
Used in construction, aggregate, road base, and occasionally in polished form for decorative landscaping or massage stones.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the oceanic crust as well as extensive continental volcanic provinces like the Columbia River Basalts.
Field identification & locations
Identified by its dark color, fine-grained texture, and high density. Commonly found in riverbeds and beaches where water action has smoothed and rounded the rock into pebbles.
