igneous
Pumice
Pumice (Felsic volcanic rock)
Hardness: 5-6 Mohs. Color: white, cream, or light grey. Luster: dull to pearly. Structure: Highly vesicular (pitted with gas bubbles). Specific gravity: very low (often floats on water).
- Hardness
- 5-6 Mohs
- Color
- white, cream, or light grey
- Luster
- dull to pearly
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 Mohs. Color: white, cream, or light grey. Luster: dull to pearly. Structure: Highly vesicular (pitted with gas bubbles). Specific gravity: very low (often floats on water).
Formation & geological history
Formed when highly pressurized, gas-rich magma is violently ejected from a volcano. The rapid cooling and depressurization trap gas bubbles, creating a frothy texture. Found in explosive volcanic regions.
Uses & applications
Used in construction for lightweight concrete, in cosmetics as an exfoliant, in horticulture for soil aeration, and industrially as a mild abrasive for polishing.
Geological facts
Pumice is the only rock that can float on water due to its extreme porosity. Massive rafts of pumice have been observed floating on the ocean after underwater volcanic eruptions.
Field identification & locations
Identified by its lightweight, sponge-like appearance and rough texture. It is commonly found in ash fall deposits or near stratovolcanoes. Collectors look for unique shapes and low density.
