Pumice

In commerce, pumice is the term applied to larger pumice stones, while pumicite consists of fine grains or ash.

The History Says

The name pumice is derived from the Latin word 'pumex,' meaning 'foam.' Pozzolan (or pozzolana) is an Italian word, named from 'Pozzuoli,' the place near Naples where pozzolan was first mined and used as cement, during Roman times.

The Present Scenario

The largest producer of pumice is Italy. Other major producers are Greece, Chile, Spain, Turkey, and the US.

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Pumice is a light and porous type of pyroclastic igneous rock. It is formed from the lava that is full of gas. During the explosive volcanic eruptions, the liquid lava is ejected in the air. As the lava hurtles through the air, it cools and the gases escape from the rock, leaving it full of holes.

Any type of igneous rock can form pumice rock, provide suitable eruptive conditions it get. It can be andesite, basalt, dacite or rhyolite. When larger amounts of gas are present in the rock, the resultant is a finger-grained variety of pumice, which is known as pumicite.

Since, pumice has no crystal structure, it is considered to be a glass. It varies in density according to the thickness of the solid material between the bubbles. Many of the samples even float in water. The rock comes in variety of colors, like white, yellowish, gray, brown, and a dull red.

Uses of Pumice

Pumice is popular in making lightweight concrete and is used as abrasive, particularly in polishes and cosmetics exfoliants. When pumice is used as an additive for cement, its fine-grained version knowns as pozzolan is mixed with lime to form a light-weight, smooth, plaster-like concrete. This type of concrete has been in use since Roman times.