The pore spaces (known as vesicles) in pumice are a clue to how it forms. The vesicles are actually gas bubbles that were trapped in the rock during the rapid cooling of a gas-rich frothy magma. The material cools so quickly that atoms in the melt are not able to arrange themselves into a crystalline structure.Thus, pumice is an amorphous volcanic glass known as a  mineraloid .he abundant vesicles in pumice and the thin walls between them give the rock a very low specific gravity. It typically has a specific gravity of less than one, giving the rock an ability to float on water.
While an electromagnetic wave is called just a disturbance, a mechanical wave is considered a periodic disturbance. Mechanical waves are also called elastic waves as their propagation depends on the elastic properties of the medium through which the waves pass.
Differences between Sound Waves And Electromagnetic Waves. 1  A Sound wave is a longitudinal wave whereas, electromagnetic waves are transverse waves. 2  Sound is a mechanical vibration that passes through a medium such as gas, liquid or solid to become a sound.aves that does not need any medium or matter to travel through, and travels through space, are called electromagnetic waves. Sound waves. Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving.