Volcanic stone gravel PUMICE

external

PUMICES and LAPILLI are products of explosive volcanic eruptions formed following a violent expansion of the gases dissolved in lavas with an acid chemical composition. The rapid cooling of the rock has prevented the crystallization of the same, trapping internally the gases and generating more or less expanded beehive minerals. During the solidification, the vapours present in the magma, suddenly released, have caused the swelling of the whole magma mass. During this phase of rapid cooling, certain differences in the physical structure of various inert volcanic materials have been released. The magma, which has originated the PUMICE, had such a chemical composition which permitted the rapid expansion of gases dissolved internally, forming a kind of foam. The rapid cooling of the lava has determined an unexpected solidification of the liquid part around the gas bubbles generating this appearance of vitreous foam of the pumice. The internal part of the rock is in fact composed of an enormous quantity of ducts having a very small/medium diameter, intercommunicating between themselves and also externally.