igneous
Polished volcanic scoria or vesicular basalt
Vesicular basalt; primarily plagioclase, pyroxene, and iron-rich glass/oxides
AI-generated identification · may be incorrectDark reddish-brown, rounded and polished, with abundant small vesicles and possible secondary mineral fillings; hardness about 5–6 Mohs, dull to slightly vitreous luster, fine-grained matrix, and no obvious cleavage. The reddish color reflects oxidation of iron-bearing minerals.
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Physical properties
Dark reddish-brown, rounded and polished, with abundant small vesicles and possible secondary mineral fillings; hardness about 5–6 Mohs, dull to slightly vitreous luster, fine-grained matrix, and no obvious cleavage. The reddish color reflects oxidation of iron-bearing minerals.
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly, trapping bubbles; later weathering oxidized the iron. Likely Cenozoic or younger, though the image alone cannot establish age or locality.
Uses & applications
Used mainly as a decorative or educational specimen; scoria is also used as lightweight aggregate, landscaping stone, and abrasive material. This polished piece has modest collecting value.
Geological facts
Vesicles distinguish scoria from ordinary massive basalt; abundant dark coloration and relatively high density distinguish it from pumice, which is usually pale and much lighter.
Field identification & locations
Common in volcanic regions such as Hawaii, Iceland, the western United States, Italy, and Japan. Identify with its bubbly texture, reddish-black basaltic appearance, and lack of sedimentary layering; a specific identification would benefit from locality data or microscopy.
