igneous
Basalt with Iron Oxidation
Extrusive Mafic Igneous Rock (composed of Plagioclase and Pyroxene)
Hardness: 6 (Mohs scale); Color: Dark grey to black matrix with yellowish-brown limonite/goethite staining; Luster: Dull/Earthy; Structure: Fine-grained aphanitic with small vesicles (holes from gas bubbles).
- Hardness
- 6 (Mohs scale)
- Luster
- Dull/Earthy
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black matrix with yellowish-brown limonite/goethite staining; Luster: Dull/Earthy; Structure: Fine-grained aphanitic with small vesicles (holes from gas bubbles).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a planet or moon. The yellowish-orange surface is due to chemical weathering where iron-rich minerals oxidize over time.
Uses & applications
Used extensively in construction as crushed stone for road base, concrete aggregate, railroad ballast, and in the production of high-strength stone wool insulation.
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 on the Moon and Mars, forming the dark lunar 'maria'.
Field identification & locations
Identify by its heavy weight (high specific gravity), fine-grained texture, and dark color often masked by rusty oxidation. Commonly found in volcanic fields or near oceanic rifts.
