igneous
Vesicular basalt (weathered scoria)
Scoriaceous basalt; chiefly plagioclase, clinopyroxene, olivine, and iron-titanium oxides
AI-generated identification · may be incorrectTypically dark gray to reddish-brown, highly vesicular, and dull to slightly glassy; hardness about 5–6 Mohs, fine-grained matrix, no prominent cleavage, and specific gravity roughly 2.4–2.8 (lower where porous). The orange-brown coloration reflects oxidation and weathering of iron-bearing minerals.
Identified More igneous →
Explore Vesicular basalt (weathered scoria) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically dark gray to reddish-brown, highly vesicular, and dull to slightly glassy; hardness about 5–6 Mohs, fine-grained matrix, no prominent cleavage, and specific gravity roughly 2.4–2.8 (lower where porous). The orange-brown coloration reflects oxidation and weathering of iron-bearing minerals.
Formation & geological history
Forms when gas-rich basaltic lava rapidly cools, preserving abundant bubbles; commonly associated with cinder cones, lava flows, and volcanic bombs, generally Quaternary to recent but potentially much older. The specimen’s weathered surface and cavities are consistent with terrestrial volcanic scoria.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, abrasive, and occasionally as a decorative or educational specimen. It has little gemstone value but can be attractive when vesicles and oxidation are pronounced.
Geological facts
Vesicles are frozen gas bubbles, not fossils or man-made holes; some cavities may later become lined with zeolite, calcite, or quartz. Scoria is generally denser and darker than pumice, which can float when fresh.
Field identification & locations
Identify by its porous volcanic texture, irregular cavities, rusty iron staining, and lack of sedimentary layering; a steel file usually scratches the softer groundmass only slightly. Common worldwide in basaltic volcanic regions, including Hawaii, Iceland, Mexico, and the western United States.
