Pumice

Hardness: 5-6 (Mohs), Color: Light gray, tan, or cream, Luster: Dull/Glassy, Structure: Highly vesicular/porous, Density: Often floats on water

Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected and cools rapidly, trapping gas bubbles. Generally from various geological ages corresponding to volcanic activity regions.

Used as an abrasive in polishing, skin exfoliation, pencil erasers, and stone-washed jeans. Also used in lightweight concrete and horticulture as a soil additive.

Pumice is the only rock that can float on water due to its incredible porosity. Massive rafts of floating pumice can be found in the ocean after large underwater volcanic eruptions.

Identify in the field by its light weight, rough texture, and many small visible pores (vesicles). Found in volcanic regions like the Cascades, Andes, or Iceland.