Basalt with Iron Oxidation

Physical Properties

Hardness: 6 (Mohs scale); Color: Dark grey to charcoal with reddish-brown oxidation streaks; Luster: Dull to sub-vitreous when wet; 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. The reddish streaks indicate secondary iron oxidation (rusting) occurring along micro-fractures during weathering.

Uses & Applications

Used in construction as aggregate, for paving, in the manufacture of rock wool insulation, and occasionally as decorative river stones in landscaping.

Geological Facts

Basalt is the most common rock type in the Earth's crust and makes up the majority of the ocean floor. It is also found extensively on the Moon and Mars.

Field Identification & Locations

Identify in the field by its heavy weight, dark color, and lack of visible crystals. This specimen is water-worn and polished, likely found in a riverbed or coastal area. Collectors should look for signs of vesicles (gas bubbles) or trapped minerals.

Identified on: 4/28/2026

Mode: Standard