igneous
Basalt (Weathered)
Basalt
Hardness: 6 (Mohs); Color: Dark grey to black interior, brown/tan weathered exterior; Luster: Dull/Earthy; Structure: Fine-grained/Aphanitic; SG: 2.8-3.0
- Hardness
- 6 (Mohs)
- Color
- Dark grey to black interior, brown/tan weathered exterior
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6 (Mohs); Color: Dark grey to black interior, brown/tan weathered exterior; Luster: Dull/Earthy; Structure: Fine-grained/Aphanitic; SG: 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 surface. This specimen shows significant oxidation (rusting) of iron-bearing minerals due to exposure to air and water.
Uses & applications
Primarily used in construction as crushed stone for road base, concrete aggregate, and railroad ballast. Fine specimens are used in landscape design.
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 in abundance on the Moon and Mars.
Field identification & locations
Identify by its heavy weight, fine-grained dark interior, and often a brown weathered 'rind'. Found worldwide in volcanic regions, such as the Deccan Traps or the Columbia River Plateau.
