igneous
Vesicular basalt (likely scoria)
Mafic volcanic rock; predominantly plagioclase, pyroxene, and volcanic glass, with possible olivine
AI-generated identification · may be incorrectDark brown to black, fine-grained and highly vesicular, with rounded gas cavities and dull to slightly glassy luster. Hardness is approximately 5–6 Mohs; cleavage is absent or not visible, and density is reduced by the vesicles.
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Physical properties
Dark brown to black, fine-grained and highly vesicular, with rounded gas cavities and dull to slightly glassy luster. Hardness is approximately 5–6 Mohs; cleavage is absent or not visible, and density is reduced by the vesicles.
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly at or near the surface, trapping bubbles; likely Quaternary or younger, though the image cannot establish age or locality.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and occasionally as a lapidary or specimen stone. Common scoria generally has modest collector value.
Geological facts
Its cavities are vesicles, not fossil holes; rusty brown coloration commonly reflects oxidation of iron-bearing minerals. The specimen may also be weathered basalt or an iron-rich volcanic fragment.
Field identification & locations
Look for a dark mafic color, abundant irregular vesicles, low relative density, and a rough frothy texture; scoria is typically lighter than solid basalt and does not fizz in dilute acid. Common worldwide near cinder cones and basaltic lava fields.
