Pumice
[3] Pumice is composed of highly microvesicular glass pyroclastic with very thin, translucent bubble walls of extrusive igneous rock.
Pumice is commonly pale in color, ranging from white, cream, blue or grey, to green-brown or black.
[9] In 1979, 1984 and 2006, underwater volcanic eruptions near Tonga created large pumice rafts that floated hundreds of kilometres to Fiji.
It has an extremely low density and is composed of a network of volcanic glass formed when the vesicles have almost completely coalesced.
[16] As described earlier pumice is produced by the eruption of explosive volcanoes under certain conditions, therefore, natural sources occur in volcanically active regions.
[17] There are large reserves of pumice in Asian countries including Afghanistan, Indonesia, Japan, Syria, Iran, and eastern Russia.
[19] Europe is the largest producer of pumice with deposits in Italy, Turkey, Greece, Hungary, Iceland, and Germany.
Large amounts of igneous rock on Lipari are due to the numerous extended periods of volcanic activity from the Late Pleistocene (Tyrrhenian) to the Holocene.
[21] One of the most famous volcanoes was Mount Mazama that erupted 7,700 years ago in Oregon and deposited 300 feet of pumice and ash around the vent.
The large amount of magma that was erupted caused the structure to collapse, forming a caldera now known as Crater Lake.
The volcano erupted in July 2012 but remained unnoticed until enormous pieces of pumice were seen to be floating on the Pacific Ocean.
[26] There is high demand for pumice, particularly for water filtration, chemical spill containment, cement manufacturing,[27] horticulture and increasingly for the pet industry.
The mining of pumice in environmentally sensitive areas has been under more scrutiny after such an operation was stopped in the U.S. state of Oregon, at Rock Mesa in the southern part of the Three Sisters Wilderness.
Ingestion of these pulverized rocks was believed to be able to soften nodules and was later used with other herbal ingredients to treat gallbladder cancer and urinary difficulties.
In Western medicine, beginning in the early 18th century, pumice ground into a sugar consistency mixed with other ingredients was used to attempt to treat ulcers mostly on the skin and cornea.
In ancient Egypt, it was common to remove all hair on the body to control lice and as a form of ritual purification, using creams, razors, and pumice stones.
"Pumice stones" are often used in beauty salons during the pedicure process to remove dry and excess skin from the bottom of the foot as well as calluses.
Finely ground pumice has been added to some toothpastes as a polish, similar to Roman use, and easily removes dental plaque build-up.
Pumice stone, sometimes attached to a handle,[33] is an effective scrubbing tool for removal of limescale, rust, hard water rings, and other stains on porcelain fixtures in households (e.g., bathrooms).
Good soil requires sufficient water and nutrient loading as well as little compaction to allow easy exchange of gases.
Pumice improves the quality of soil because of its porous properties; water and gases can be transported easily through the pores and nutrients can be stored in the microscopic holes.
The addition of pumice to soil improves and increases vegetative cover as the roots of plants make slopes more stable therefore it helps reduce erosion.
It is often used on roadsides and ditches and commonly used in turf and golf courses to maintain grass cover and flatness that can degrade due to large amounts of traffic and compaction.
[18] A fine-grained version of pumice called pozzolan is used as an additive in cement and is mixed with lime to form a light-weight, smooth, plaster-like concrete.
Roman engineers utilized it to build the huge dome of the Pantheon with increasing amounts of pumice added to concrete for higher elevations of the structure.
