igneous
Basalt Pebble
Basalt
Hardness: 6 (Mohs); Color: Dark grey to black; Luster: Dull or earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs)
- Color
- Dark grey to black
- Luster
- Dull or earthy
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Physical properties
Hardness: 6 (Mohs); Color: Dark grey to black; Luster: Dull or earthy; Crystal structure: 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 very near the Earth's surface. Common in oceanic crust and volcanic regions.
Uses & applications
Used primarily in construction aggregate, road base, concrete, and as a decorative stone in landscaping.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the surface of the Moon and Mars.
Field identification & locations
Identify by its dark color, fine grain, and weight. Commonly found along riverbeds, beaches, and in volcanic fields. Usually rounded when found as pebbles due to water erosion.
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