mysqlClass Error 9 in file extras/autoload.inc.php, line 72:
Error #8192: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead
pumice

pumice

SRI Petrography ID: 33

Names

[de] Bimsstein
[en] pumice

Description

pumice is a very fine grained (often the grains are not visible by naked eye), light coloured, light weight, highly vesicular acidic volcanic glass.
Pumice is a special kind of volcanic glass formed by the solidification of lavafoam permeated with gas bubbles. The fineness of pumice is determined by the viscosity of the lava, the quantity of water vapor and gas and the cooling rate. Large amounts of gas generate a very fine-grained variety known as pumicite.
Chemically the composition of pumice is similar to that of granite.
Due to its porous nature pumice has low density (< 1) and insulating properties. It is used in the construction industry, in light-weight structural concrete, plaster aggregate and loose fill insulation.

Pumice is also used as an abrasive and is included in many scouring preparations and in finishing furniture. As additive for cement and concrete is has already been used in Roman times.
Pumice usually floats and can be carried great distances by ocean currents and winds due to its low density and high content of air chambers.

Color

white, brown, light grey

Grain Size

fine grained, glassy

Texture

porous volcanic glass

Minerals

glass

Occurences

Pumice can be found in volcanic areas throughout the world, e.g. Italy, Greek islands, Iceland

Comments

A coarser-grained rock with fewer and larger air spaces (pores) is called scoria.

Classification

Class

IGNEOUS ROCKS

Broader Terms

pyroclastic rocks