igneous
Vesicular volcanic rock, likely pumice or scoriaceous basalt
Pumice (highly vesicular volcanic glass) or vesicular basalt; exact identification requires testing
AI-generated identification · may be incorrectLight gray, highly porous, rough and dull, with abundant rounded cavities (vesicles); likely hardness about 5–6 for basaltic material, while pumice may abrade easily. No visible crystals are confidently identifiable; apparent dark areas may be basaltic matrix or weathering.
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Physical properties
Light gray, highly porous, rough and dull, with abundant rounded cavities (vesicles); likely hardness about 5–6 for basaltic material, while pumice may abrade easily. No visible crystals are confidently identifiable; apparent dark areas may be basaltic matrix or weathering.
Formation & geological history
Forms when gas-rich lava rapidly cools, trapping bubbles during volcanic eruptions; likely Quaternary or younger, though age cannot be determined visually. Pumice is commonly rhyolitic to dacitic, whereas darker, denser scoria is basaltic.
Uses & applications
Pumice is used as an abrasive, lightweight aggregate, horticultural medium, and concrete additive; scoria is used for landscaping, drainage, and construction aggregate. Ordinary hand specimens generally have little monetary value.
Geological facts
The key distinction is density: pumice commonly floats in water, while scoria or vesicular basalt usually sinks. The specimen’s relatively dark, irregular appearance favors scoria/vesicular basalt over pale pumice.
Field identification & locations
Common around volcanic fields, cinder cones, lava flows, and beaches receiving volcanic debris. Test density, streak, and magnetism; a fresh broken surface and a loupe can help distinguish glassy pumice from crystalline basalt.
