igneous
Basalt with Iron Oxidation
Mafic Igneous Rock (primarily Plagioclase and Pyroxene)
Hardness: 6 (Mohs scale); Color: Dark grey to black with reddish-brown oxidation crust; Luster: Dull to earthy; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black with reddish-brown oxidation crust
- Luster
- Dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black with reddish-brown oxidation crust; Luster: Dull to earthy; 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 at or very near the Earth's surface. It can be found in oceanic crust, volcanic islands, and continental flood basalts.
Uses & applications
Used extensively in construction as an aggregate for road base, concrete, and railroad ballast. Fine-grained specimens are also used for stone carving and as thermal insulators.
Geological facts
Basalt is the most common rock type in the Earth's crust and also covers large areas of the Moon (the Lunar Maria), Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture. Reddish staining indicates weathering or iron content. Commonly found in volcanic regions or as rounded river cobbles.
