igneous
Basalt
Basalt
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to matte; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0; Composition: Plagioclase feldspar and pyroxene.
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull to matte
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to matte; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0; Composition: Plagioclase feldspar and pyroxene.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. It is the most common volcanic rock on Earth, often found in oceanic crust and lava flows.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for pavers or countertops.
Geological facts
Basalt also makes up most of the ocean floors and is found on the Moon and Mars. It can form unique hexagonal columns during cooling, such as those at the Giant's Causeway.
Field identification & locations
Identify by its heavy weight (high density), dark color, and lack of visible crystals to the naked eye. Commonly found in volcanic regions and shorelines.
