Igneous

Pumice

Pumicite (Amorphous Volcanic Glass)

Hardness: 5-5.5 (though brittle); Color: White, light gray, or cream; Luster: Dull to pearly; Structure: Vesicular (highly porous/bubbly); Specific Gravity: 0.25-1.2 (low enough to float on water initially).

Hardness: 5-5
Color: White, light gray, or cream
Luster: Dull to pearly

Identified March 17, 2026More igneous →

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Physical properties

Formation & geological history

Formed during explosive volcanic eruptions when highly pressurized, gas-rich lava is ejected into the air. The rapid cooling and depressurization trap gas bubbles in the solidifying glass. Found in volcanic regions worldwide.

Uses & applications

Used as an abrasive in polishing, skin exfoliation (pumice stones), heavyweight concrete additives, horticultural soil amendments for drainage, and in the production of stone-washed jeans.

Geological facts

Pumice is the only rock known to float on water for extended periods. Large eruptions can create 'pumice rafts' in the ocean that are hundreds of miles long and can float for years.

Field identification & locations

Identify by its extremely lightweight feel and visible holes (vesicles). It is commonly found in areas such as the Ring of Fire or the Mediterranean. Collectors should look for unique glass-string textures.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous