igneous
Light-colored igneous rock, likely pumice or vesicular rhyolite
Primarily silica-rich volcanic glass and feldspar; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectPale gray, fine-grained and irregular, with apparent small cavities and a dull to weakly vitreous luster. Likely hardness about 5–7 Mohs if rhyolitic, or 5–6 if pumice; cleavage is absent or poorly developed and specific gravity may be low if highly vesicular.
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Physical properties
Pale gray, fine-grained and irregular, with apparent small cavities and a dull to weakly vitreous luster. Likely hardness about 5–7 Mohs if rhyolitic, or 5–6 if pumice; cleavage is absent or poorly developed and specific gravity may be low if highly vesicular.
Formation & geological history
Formed when silica-rich volcanic magma cooled rapidly during an eruption, trapping gas bubbles; likely Cenozoic or younger, though age cannot be determined visually. Common in volcanic ash, lava-flow, and pyroclastic deposits.
Uses & applications
Pumice is used as an abrasive, lightweight aggregate, exfoliating stone, and horticultural additive; rhyolite is mainly a decorative or educational specimen and occasionally crushed aggregate.
Geological facts
The specimen’s porous, crumbly appearance is consistent with pumice, but the image is too small and blurred for a confident distinction from weathered rhyolite or tuff.
Field identification & locations
Check whether it floats or is exceptionally lightweight, which supports pumice; a glassy fracture and abundant vesicles are diagnostic. Common worldwide in volcanic regions, including Italy, Iceland, the western United States, and New Zealand.
