igneous
Weathered volcanic rock, likely basaltic scoria
Vesicular basalt/scoria; primarily plagioclase, pyroxene, olivine, and iron oxides
AI-generated identification · may be incorrectDark tan-brown, fine-grained and weakly vesicular, with dull to earthy luster and irregular fracture; estimated Mohs hardness 5–6 and specific gravity about 2.4–2.9. The rusty color likely reflects surface oxidation and weathering.
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Physical properties
Dark tan-brown, fine-grained and weakly vesicular, with dull to earthy luster and irregular fracture; estimated Mohs hardness 5–6 and specific gravity about 2.4–2.9. The rusty color likely reflects surface oxidation and weathering.
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly, trapping vesicles; subsequent weathering produced the brown iron-oxide coating. Such rocks are generally Cenozoic to Recent, though the exact age cannot be determined from the image.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and occasionally abrasive or decorative stone; this small weathered specimen has little jewelry value.
Geological facts
Scoria is typically more vesicular and lighter than ordinary basalt, while basalt is denser and fine-grained. The visible cavities and iron staining support a volcanic origin, but the specimen could also be weathered vesicular basalt or an iron-rich volcanic cobble.
Field identification & locations
Common in volcanic fields, lava flows, cinder cones, and beaches or streambeds draining volcanic terrain. Check for a black fine-grained interior, vesicles, and a streakless or pale-gray powder; a magnet may respond weakly because of magnetite.
