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.
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.
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