igneous
Basalt
Basalt
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Aphanitic (fine-grained), typically containing minerals like plagioclase feldspar, pyroxene, and olivine.
- Hardness
- 6 on the Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Aphanitic (fine-grained), typically containing minerals like plagioclase feldspar, pyroxene, and olivine.
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the Earth's surface, typically originating from volcanic eruptions.
Uses & applications
Used in construction, road aggregate, railroad ballast, production of stone wool insulation, and as dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans and also forms massive volcanic features like the Giant's Causeway in Northern Ireland and the Columbia River Plateaus.
Field identification & locations
Can be identified in the field by its dark color, fine-grained texture (often requiring a hand lens to see individual crystals), and heavy density. It is commonly found globally in volcanic regions and oceanic crusts.
