igneous
Basalt with Iron Oxidation
Vesicular Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 5-6 Mohs. Color: Dark grey to black with reddish-orange iron oxide staining. Luster: Dull/Earthy. Structure: Fine-grained (aphanitic) with small vesicles (gas bubbles). Specific Gravity: High (approx 2.8-3.0).
- Hardness
- 5-6 Mohs
- Color
- Dark grey to black with reddish-orange iron oxide staining
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Dark grey to black with reddish-orange iron oxide staining. Luster: Dull/Earthy. Structure: Fine-grained (aphanitic) with small vesicles (gas bubbles). Specific Gravity: High (approx 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 surface suggests subaerial weathering where iron minerals have oxidized into limonite or hematite.
Uses & applications
Used primarily in construction (crushed stone), road base, concrete aggregate, and sometimes in landscaping or as aquarium stones.
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.
Field identification & locations
Identify by its dark color, heavy weight for its size, and fine-grained texture. It will not react with acid. Commonly found in volcanic fields, oceanic islands (like Hawaii), and flood basalt provinces.
