Basalt with Iron Oxidation

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.

Identified on: 4/13/2026

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