igneous
Pumice (likely)
Pumice, vesicular volcanic glass; typically silica-rich rhyolitic to dacitic composition
AI-generated identification · may be incorrectPale tan, rough and highly porous with abundant gas-bubble cavities and a dull to slightly glassy luster. Hardness is variable, roughly 5–6 Mohs, and it has no distinct crystal structure or cleavage; the small specimen is not enough to confirm identification.
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Physical properties
Pale tan, rough and highly porous with abundant gas-bubble cavities and a dull to slightly glassy luster. Hardness is variable, roughly 5–6 Mohs, and it has no distinct crystal structure or cleavage; the small specimen is not enough to confirm identification.
Formation & geological history
Forms when gas-rich volcanic lava froths and cools rapidly during an explosive eruption. Its age depends on the source eruption; pumice occurs in volcanic deposits of many ages.
Uses & applications
Used as a lightweight aggregate, abrasive, polishing stone, and horticultural soil additive; attractive pieces may be collected, but this fragment has little gem value.
Geological facts
Pumice is so vesicular that large pieces can float on water, though this small fragment may not. Similar porous volcanic rocks, especially scoria, can look alike.
Field identification & locations
Look for a lightweight, frothy texture with many rounded pores; scoria is usually darker and denser. Pumice occurs near explosive volcanoes and in ash-flow or pumice-fall deposits worldwide.
