igneous
Weathered reddish-brown rock fragment
Probably altered basalt or fine-grained volcanic rock; exact identification requires testing
AI-generated identification · may be incorrectDark reddish-brown, dull to slightly earthy luster, fine-grained and irregularly fractured, with apparent vesicular or weathered cavities. Estimated Mohs hardness 5–6; cleavage absent; specific gravity likely about 2.7–3.1.
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Physical properties
Dark reddish-brown, dull to slightly earthy luster, fine-grained and irregularly fractured, with apparent vesicular or weathered cavities. Estimated Mohs hardness 5–6; cleavage absent; specific gravity likely about 2.7–3.1.
Formation & geological history
Likely volcanic rock formed from cooling lava, later altered by oxidation and weathering; its geological age cannot be determined from the photograph. The cavities may reflect gas bubbles or differential weathering.
Uses & applications
Useful mainly as a teaching or collecting specimen; basalt and related rocks are widely used as aggregate, roadstone, riprap, and construction material.
Geological facts
The reddish coloration commonly comes from iron oxidation, producing hematite- or limonite-stained surfaces. A fresh broken surface would help distinguish basalt from sandstone, slag, or iron-rich sedimentary rock.
Field identification & locations
Common in volcanic terrains worldwide, including Hawaii, Iceland, the Pacific Northwest, and many continental flood-basalt regions. Check texture with a hand lens, streak, magnetism, acid reaction, and hardness; the image alone is insufficient for a precise species-level identification.
