igneous
Basalt with Iron Oxidation
Extrusive Igneous Rock (Mafic)
Hardness: 6 on the Mohs scale; Color: Dark grey to black with brownish-orange patches due to iron oxidation; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), usually microscopic crystals.
- Hardness
- 6 on the Mohs scale
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6 on the Mohs scale; Color: Dark grey to black with brownish-orange patches due to iron oxidation; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), usually microscopic crystals.
Formation & geological history
Formed from the rapid cooling of low-viscosity, iron- and magnesium-rich lava exposed at or very near the Earth's surface, often originating from volcanic eruptions.
Uses & applications
Used in construction, aggregate for road building, crushed stone, and sometimes as dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans and makes up most of the oceanic crust as well as volcanic islands like Hawaii and Iceland.
Field identification & locations
Identify by its dark, fine-grained matrix and water-worn smooth texture if found in riverbeds or beaches; often shows rust-colored weathering where iron minerals have oxidized.
