0 a type of grey, light stone that is used in pieces or as a powder for rubbing things to make them smooth: --
For this purpose biofilms were grown as autotrophic and heterotrophic communities on pumice in an airlift loop reactor.
The internal structure of the bedforms is massive, although openwork clusters of pumice occur at the crest and on the lee-side.
The alkali basalt lithic breccias pass abruptly upwards into banded pumice-bearing ignimbrite.
Lithic fragments are commonly embedded in the larger pumices.
Concentrations of pumice occur locally in the upper 20-30 cm of the ignimbrite.
Particle-supported autotrophic biofilms were cultivated in external-loop airlift reactors at different pumice concentrations.
In the sixth zone, an abrupt change to greyish pumice is encountered, and no crystals are seen.
These tuffs are all considered to be ash flow deposits because they are unbedded and contain well-developed eutaxitic foliation and pumice pseudomorphs locally.
