How Is Pumice Processed?
Pumice is a powdery, porous type of volcanic stone, so lightweight it can float on water. The Mineral Information Institute states pumice is created when super-heated lava is ejected from the pressurized depths of the volcano with such rapidity that the lava is subject to abrupt cooling and depressurization. Gas bubbles of carbon dioxide then form in the volcanic stone and harden, creating a stone with a honeycomb structure of hard "bubbles" which has many uses.
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Uses of Pumice
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According to the Mineral Information Institute, coarse ground or coarse-processed pumice, particularly Italian pozzolan, is used to make concrete and building blocks known as "breeze blocks," used for insulation. Coarse-processed pumice is also used as an abrasive in cleansers, heavy-duty soaps, metal polishes and to create a "stone-washed" effect on blue-jean denim. The beauty and skincare industry uses a more finely-processed pumice as a skin exfoliant. Different uses require different degrees of refining and processing pumice stone.
History
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Ancient Romans used pumice to create a lightweight, durable concrete, according to the Mineral Information Institute. This concrete was used to build aqueduct arches, as well as domes, including the dome of the Pantheon, built in 120 AD, according to Monolithic.com. The Romans processed pumice for concrete by mixing chunks of pumice with wet lime and volcanic ash, creating a low water mixture. In addition, unprocessed pumice stones were also used by Greek and Roman cultures to remove unwanted body and facial hair.
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Building Abrasive Use
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According to the National Park Service, pumice and volcanic ash are considered "soft" abrasives which can be safely used to clean certain historic buildings. The pumice used for this type of abrasive must be processed by being first broken down and then ground into fine particles before it can be used, according to the National Park Service. Abrasive cleaning is used to remove dirt, soot, rust stains on stone, brick and concrete structures; it is not recommended for stucco, adobe or painted surfaces.
Skin Exfoliant
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Pumice, which is processed by being finely ground, is used for skincare and beauty products. Industrial grinding techniques are able to refine pumice down into grades of 1 millimeter or approximately 0.0393 inches, all the way up to 5 millimeters---roughly 1/5 of an inch. Only pumice that is processed down to the 1 to 5 millimeter range is used in commercial preparations to exfoliate and cleanse skin, and to clean and polish teeth.
Pumice Stones
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In addition to commercial preparations, pieces of actual pumice can also be used to slough off dead skin cells and remove callouses, particularly from the feet. Pumice stones for this type of use are marketed as pumice sponges, pumice sticks and buffing stones. They are sold at hardware stores, as well as in the cosmetic aisle of most commercial drugstores. This type of pumice is unprocessed, except for filing it into shape.
Where Pumice Is Produced
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Due to its long-existing volcanic history, Italy is the largest worldwide supplier of pumice varieties, including pozzolan, according to the Mineral Information Institute. Spain, Greece, Turkey, New Zealand and Chile also produce and process large amounts of pumice. In the United States, pumice is produced in California, Arizona, New Mexico and Oregon, and Hawaii is also a source of pumice.
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References
- Photo Credit texture pumice stone image by Petr Gnuskin from Fotolia.com
