igneous

Pumice

Pumice (Vesicular Rhyolite/Andesite)

Hardness: 5-6 Mohs (though brittle); Color: white, cream, or light grey; Luster: dull to pearly; Structure: highly vesicular (porous); Cleavage: none; Specific Gravity: less than 1.0 (floats in water).

Hardness: 5-6 Mohs (though brittle)
Color: white, cream, or light grey
Luster: dull to pearly

Identified May 18, 2026More igneous →

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Physical properties

Formation & geological history

Formed during explosive volcanic eruptions when pressurized gas is trapped in rapidly cooling lava, creating a frothy glass. Typically found in volcanic regions worldwide.

Uses & applications

Used as an abrasive in cleaning products, cosmetic exfoliants (pumice stones), lightweight concrete aggregate, and in stonewashing denim.

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 thousands of miles.

Field identification & locations

Identify by its extremely lightweight feel, porous appearance, and ability to float. Commonly found on beaches near volcanic island arcs or near continental volcanoes.

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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