Pumice rock

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Pumice rock consists of highly porous, bubbly volcanic glass. The gas bubbles (frothy texture) makes the rock lightweight. It will float on water for some time.

Igneous: Produced when erupting magma is charged with gases (thus technically a volcanic igneous rock).

Source location: Waikato.

Sizes: Choose from dropdown menu Shelf specimen (suitable for display), or Hand specimen (fits in palm of hand), or Small specimen.

Note: Images are examples of specimens only. Sizes and shapes will vary.

More detail


Pumice is a volcanic rock characterised by its porous and frothy structure. It forms when frothy lava rapidly cools and solidifies, trapping gas bubbles within its matrix.


Volcanic igneous.

Physical properties of pumice

  • Colour: Typically light grey or white in colour.
  • Lustre: Dull or matte.
  • Porosity: Highly porous, with numerous interconnected voids or vesicles.
  • Density: Very low, ranging from 0.25 to 0.65 grams per cubic centimetre.
  • Hardness: Around 5 to 6 on the Mohs scale.

General properties of pumice

  • Porous Structure: A distinctive feature is its porous structure, resulting from the entrapment of gas bubbles during volcanic eruptions.
  • Lightweight: Exceptionally lightweight due to its high porosity and low density.
  • Floatability: Can float on water due to its low density, making it useful in applications where buoyancy is desired.
  • Friable: Friable, meaning it can be easily crumbled or powdered with minimal force.
  • Insulating Properties: Exhibits excellent insulation properties, both thermal and sound, due to its high porosity.

Uses of pumice in New Zealand and worldwide

  • Early Māori: Pumice (tāhoata) was used to make floats (pōuto) to support the top edge of fishing nets.
  • Abrasive: Used as an abrasive material in various applications, such as polishing, exfoliating skin, and cleaning surfaces.
  • Horticulture: Widely used in horticulture and gardening as a soil amendment to improve drainage and aeration.
  • Lightweight Concrete: Used as an aggregate in lightweight concrete production, creating structures with reduced weight.
  • Filtration Media: Employed as a filtration media in water and wastewater treatment systems, removing impurities and particulates.
  • Footwear and Insulation: Used in the production of lightweight footwear and insulation materials due to its lightweight and insulating properties.
  • Personal Care Products: Utilised in personal care products, such as foot scrubs and exfoliating soaps.
  • Art and Craft: Used by artists and crafters for sculpting, painting, and creating textured surfaces.