igneous
Possible vesicular basalt or scoriaceous volcanic rock
Basaltic scoria; chiefly plagioclase, pyroxene, and olivine with volcanic glass
AI-generated identification · may be incorrectDark gray to rusty brown, rough and fine-grained with possible vesicles; typically dull to slightly glassy, hardness about 5–6 Mohs, no obvious cleavage, and specific gravity roughly 2.2–3.0. The orange-brown areas likely represent oxidation of iron-bearing minerals.
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Physical properties
Dark gray to rusty brown, rough and fine-grained with possible vesicles; typically dull to slightly glassy, hardness about 5–6 Mohs, no obvious cleavage, and specific gravity roughly 2.2–3.0. The orange-brown areas likely represent oxidation of iron-bearing minerals.
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly at or near the surface, trapping bubbles; commonly Quaternary to Recent, though basalt occurs throughout geologic time. Exact identification is limited by the small image and lack of scale.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, and sometimes in horticulture; usually has little jewelry value.
Geological facts
Scoria is vesicular and relatively lightweight, whereas dense basalt has few or no visible cavities; a reddish surface commonly reflects weathering or oxidation.
Field identification & locations
Look for a black-to-red volcanic texture, tiny holes, and a nonmetallic appearance; common around cinder cones, lava flows, and volcanic fields worldwide. Value is generally $1–$10 for a common hand specimen, or up to about $20 if labeled and display-quality.
