Pumice is a rock magmatic effusive , very light for the very high porosity.
The period from the geological point of view is generic and refers to the particular texture of porous rock. It is formed mainly by explosive eruptions , and then by acid magma , or felsic silicate ( but there are also a part- mafic component ) and the porosity is due to the formation of gas bubbles in the foam -like structure in the glassy matrix of the rock .
The rapid cooling retains vesicular structure ( forming the 90 % of the volume while the slag is less vesicular volcanic ) , and the solid rock is composed of amorphous , rarely with a small crystalline component . The solid mass is at the end consists predominantly of silica, dissolved with various metal oxides (aluminum , titanium , iron , manganese and others). Because of its high porosity is the only stone floating in the water.
The volume of the sample , however, must be over 5-7 cm ³. Having a density less than water , pumice floats based on its cell structure spherical ( rounded ), but communicating with each other in most cases by an incomplete closure, those toward the inside of the piece in question are not flooded forcing the stone to float.
Remove calluses and dead skin of the feet of the body.
weight 56 gr