igneous

Pumice

Pumice (volcanic glass with vesicular texture)

Hardness: 5-6 (Mohs scale), though prone to crumbling; Color: Cream, light gray, or tan; Luster: Dull to pearly; Structure: Amorphous/Vesicular (porous); Specific Gravity: 0.25-0.9 (often floats on water).

Hardness: 5-6 (Mohs scale), though prone to crumbling
Color: Cream, light gray, or tan
Luster: Dull to pearly

Identified March 15, 2026More igneous →

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Physical properties

Formation & geological history

Formed during explosive volcanic eruptions when highly pressurized, gas-rich rhyolitic or dacitic lava cools rapidly, trapping gas bubbles (vesicles) as the pressure drops suddenly.

Uses & applications

Used as an abrasive in skincare (exfoliation), heavy-duty cleaning, stonewashed denim production, and as a lightweight aggregate in concrete and landscaping.

Geological facts

Pumice is the only rock that can float on water due to its air-filled pores. Large eruptions can create 'pumice rafts' that drift across oceans for years and can even be seen from space.

Field identification & locations

Identify in the field by its sponge-like appearance and surprisingly light weight. It is commonly found near volcanic arcs and active or dormant explosive volcanoes like those in Italy, Turkey, and the USA.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

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Magnetite

Magnetite (Fe3O4)

mineral