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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
Structure
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.
Type
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.