pumice

Technical Data

-Chemical composition

Hekla pumice belongs to the dacite group of volcanic rocks

SiO2 66,29%
TiO2 0,58%
Al2O3 15,90%
Fe2O3 1,85%
FeO 3,26%
MnO 0,13%
MgO 0,67%
CaO 2,70%
Na2O 3,25%
K2O 2,27%
P2O5 0,50%
H2O+ 1,26%
H2O- 0,18%
LOI 1,40%

No radioactive radiation was detected in radiation tests that were carried out on Hekla pumice.

-Physical Properties

Loose dry bulk density: 0,26-0,49 kg/dm3
Depending on grainsize distribution

Loose wet bulk density: 0,54 - 0,72 kg/dm3
Depending on grainsize distribution and water content

Specific gravity of glass: 2,56

Heat conductivity: 0,07 - 0,10 kcal/m h ℃


Saturation - water, volume:

1 - 2 mm 62%
2 - 4 mm 60%
4 - 8 mm 53%
8 - 12 mm 52%


Glass and pores in 5 - 10 mm pumice, volume:

Glass 25%
Closed pores 24%
Open pores 51%

-Minerological Composition

The pumice is mostly glass due to the mode of formation, i.e. consolidation of molten silicates. Only minor quantities of chrystalline material are found in the pumice. The pumice is free from clay minerals, gypsum, sulfur and fibrous minerals. Quartz and crystobalite are not traceable by conventional x-ray diffraction analysis.

Glass 95,4%
Plagioclase 3,6%
Pyroxene 0,2%
Olivine 0,5%
Magnetite 0,3%


Fragments of basalt and andesite are embedded in the pumice layers. Most of these fragments can be removed in a washing process.