A volcanic rock that consists of highly vesicular rough-textured volcanic glass in powder or dust form. It is also known as a pumice stone. Light-colored stone may or may not have crystals. The volcanic rock that is different than pumice vesicular rock is known as scoria. Scoria has dark-colored and denser, thicker walls and has more giant vesicles as compared to a pumice stone. It takes birth, when the highly pressurized, superheated rock ejects from a volcano. Rapid depressurization and rapid cooling give pumice stone unusual foamy configuration.
There is an appearance of bubbles which is because of lowering the solubility of gases dissolved in lava. This depressurization creates bubbles that make gases absolve rapidly. It appears the same as when a carbonated drink is opened having co2.
Pyroclastic glass, a highly microvesicular stone, is its main component . It consists of thin translucent bubble wall of extrusive igneous rock . Its wide variety of light-colored ranging from white, cream, blue or grey, to green-brown or black. Bubbles usually fixes themselves inside viscous magma as it cools down to the glass. Bubbles generates when volcanic gases absolve from viscous magma. It is the product of explosive eruptions . And these are common forms area in the upper part of silicic lava.
It has a property to float over water because of its high porosity property of 64-85% by volume. Scoria can sink rapidly, but pumice do not. There is a difference of viscosity of magma that forms the stone. Scoria generates from lower viscosity magma. Its finer grained variety of is known as pumice. Its generation takes more massive amount of gas present in the stone.
It has no crystal present in it that is why volcanic glass portray its definition. The density of pumice varies according to solid material present between bubbles. Several marine species get the support of it, to float. Volcanic eruption near Tonga in the year 1979, 1984, and 2006 created large pumice rafts that floated hundreds of kilometers to Fiji.
There are broadly two main type vesicles present in it. Silky and fibrous fabric generatesfrom a tubular type of microvesicles. Due to high vapor pressure vesicles turn their shapes from subspherical to spherical during the eruption.
Name Of Pumice Stone
There is a foamy appearance of igneous rock which builds up the pumice stone. Latin words ‘pumas’ which means the foam is the idea from where pumice stone derived its name from. Pumice stone formation is still unclear up to some extent. ‘Spuma Maris ‘is a Latin word which means foam of the sea. The earlier pumice stone have puma Maris as its name, because of its frothy property to make sea surface look hardened. Because of its vesicular property, it is also known as ‘lapis spongiae.’