igneous
Basalt with Iron Oxide staining
Mafic Igneous Rock (primarily Plagioclase and Pyroxene)
Hardness: 6.0; Color: Dark grey to black with reddish-brown oxidation; Luster: Dull to earthy; Structure: Fine-grained (aphanitic); Cleavage: None; Specific Gravity: 2.8-3.0.
- Hardness
- 6
- Color
- Dark grey to black with reddish-brown oxidation
- Luster
- Dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black with reddish-brown oxidation; Luster: Dull to earthy; Structure: Fine-grained (aphanitic); Cleavage: None; 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 orange-brown spots are due to the oxidation of iron minerals (weathering).
Uses & applications
Commonly used as aggregate in construction (roads/concrete), industrial stone, and occasionally for basalt fiber or landscaping.
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 common on the Moon and Mars.
Field identification & locations
Identify by its heavy weight relative to size, dark color, and lack of visible crystals. Commonly found in volcanic regions or as river stones.
