PUMICE
Pumice
is a distinctively frothy-textured, felsic, extrusive igneous rock.
Frothy textured igneous rocks have large numbers of tiny holes formed by the
presence of many gas bubbles in the original volcanic lava. If cooling
& solidification was completed before all the gas bubbles escaped to the
lava surface, the result is a rock with lots of empty space (porosity).
Pumice is actually a volcanic glass having a frothy
texture. The solid portions of pumice are not crystalline. So,
pumice has no minerals - it has the elemental chemistry of granite & rhyolite,
but it doesn’t have any minerals.
Pumice is typically whitish, light grayish, or very
light brown in color. Most pumice samples are so lightweight that they
float on water. After the August 1883 eruption of Krakatoa in Indonesia,
sailors observed pumice floating in the Indian Ocean for many months.
Pumice is typically encountered in the form of small
chunks littering the land surface around eruptive centers. They typically
fall to Earth and form air fall pumice deposits.
Pumice
Pumice
Pumice