This is a porous rock with the composition of rhyolite. It contains minute crystals of various silicate minerals, such as feldspar and ferro-magnesians, and also has a considerable amount of glass.

TEXTURE Pumice usually tends to be used as a textural term—applied to vesiculated lavas that may resemble froth or foam. This rock has a highly scoriaceous texture, with many hollows and cavities.
The vesicles sometimes join to form elongated passages and tubes throughout the rock. Zeolites may fill these cavities. The density of pumice is so low that it can easily float in water.

ORIGIN Forms as frothy lavas associated with rhyolitic volcanic eruptions. When erupted into the ocean, patches may drift for great distances. Pumice can also be produced by land-bound volcanic eruptions.

Group: IGNEOUS

Origin: Extrusive

Grain size: Fine

Crystal shape: Anhedral

Classification: Felsic to mafic

Occurrence: Volcano

Color: Medium