igneous
Basalt with Iron Oxides
Mafic Igneous Rock (Mafite)
Hardness: 6-7 Mohs; Color: Dark grey to black with reddish-brown oxidation; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic) or vesicular; Specific gravity: 2.8–3.0.
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black with reddish-brown oxidation
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black with reddish-brown oxidation; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic) or vesicular; Specific gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The reddish spots indicate secondary oxidation (weathering) of iron minerals.
Uses & applications
Commonly used in construction as aggregate, road base, concrete, and railroad ballast. Occasionally used in stone masonry.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture. Reddish staining indicates exposure to air and water which oxidizes the iron content.
