igneous
Basalt with Iron Oxidation
Extrusive mafic volcanic rock
Hardness: 5-6 Mohs; Color: dark grey to black with orange-brown iron staining; Luster: dull to sub-metallic; Crystal structure: aphanitic (fine-grained); Specific gravity: 2.8–3.0
- Hardness
- 5-6 Mohs
- Color
- dark grey to black with orange-brown iron staining
- Luster
- dull to sub-metallic
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Physical properties
Hardness: 5-6 Mohs; Color: dark grey to black with orange-brown iron staining; Luster: dull to sub-metallic; Crystal structure: aphanitic (fine-grained); Specific gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. The orange patches indicate secondary weathering and oxidation of iron-bearing minerals like olivine or pyroxene.
Uses & applications
Used primarily in construction aggregate, road base, concrete and asphalt filler, and high-quality railroad ballast.
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, Mars, and Venus.
Field identification & locations
Identify in the field by its dark color, heavy weight for its size, and absence of large visible crystals. Look for vesicles (gas bubbles) or rusty weathering surfaces. Commonly found in volcanic regions and coastal areas.
