Volcanic pumice is a stone age tool for the 21st century, ideal for filing down foot calluses the time-honored way. Pumice forms when escaping gasses in airborne molten lava create solid foam, thus forming one handy elemental tool. 

Callus removal: Soak and lather well to soften skin. Wet stone. Finding smoothest work face or point, scrub gently, increasing pressure as attune to process. Rinse often to slough away dead skin -- pumice works with liquid. Remove thicker calluses over time. With patience you'll file away gnarliest "alligator skin." Finish with favorite moisturizer.

Pumice Care: To unclog residue buildup, soak in hot soapy water. Scrub with wire brush, rinsing often. Handle with care; rocks can fracture if dropped. Dry in sun to purify, re-energize and restore buoyancy.