igneous
Basalt Beach Pebble
Basalt (Aphanitic Mafic Volcanic Rock)
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic; 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 very near the Earth's surface. This specimen has been rounded and smoothed by water erosion (wave action).
Uses & applications
Used in construction for road base, concrete aggregate, and railroad ballast, or polished for decorative garden stones and massage therapy.
Geological facts
Basalt is the most common rock in Earth's crust and also makes up the majority of the ocean floor and large parts of the Moon and Mars.
Field identification & locations
Identify by its weight, dark color, and fine-grained texture. Commonly found on volcanic coastlines or in glacial till across the Pacific Northwest and Atlantic Canada.
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