igneous
Vesicular volcanic rock, likely pumice or scoria
Pumice (highly vesicular rhyolitic–andesitic volcanic glass) or scoria (vesicular basaltic–andesitic rock)
AI-generated identification · may be incorrectLight gray to tan, strongly porous, dull to slightly vitreous; hardness roughly 5–6, with irregular fracture and no visible cleavage. The abundant vesicles indicate gas bubbles trapped during rapid cooling; apparent metallic flecks may be reflective glass or weathering minerals.
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Physical properties
Light gray to tan, strongly porous, dull to slightly vitreous; hardness roughly 5–6, with irregular fracture and no visible cleavage. The abundant vesicles indicate gas bubbles trapped during rapid cooling; apparent metallic flecks may be reflective glass or weathering minerals.
Formation & geological history
Formed when gas-rich lava erupted explosively and quenched rapidly, commonly during volcanic eruptions in the Quaternary or older volcanic periods. The image alone cannot reliably distinguish pumice from scoria or exclude weathered industrial slag.
Uses & applications
Pumice is used as an abrasive, lightweight aggregate, soil amendment, and exfoliant; scoria is used for landscaping, drainage, and construction aggregate. Common specimens generally have little commercial value.
Geological facts
Pumice can float when its interconnected pores are abundant; scoria is typically darker, denser, and basaltic. A magnet response or glassy metallic sheen could indicate slag rather than natural volcanic rock.
Field identification & locations
Look for natural vesicles, very low density, sharp glassy edges, and lack of uniform bubbles; test streak, density, and magnetism. Common around volcanic regions worldwide, including the Pacific Rim, Mediterranean, and Iceland.
