PUMICE

الوصف

General Chemical Composition of Pumice
 ****5% SiO2  ****7% Al2O3  **3% Fe2O3 **2% CaO
 **8% Na2O-K2O

Pumice is widely used to make lightweight concrete or insulative low-density cinder blocks. When used as an additive for cement, a fine-grained version of pumice called pozzolan is mixed with lime to form a light-weight, smooth, plaster-like concrete. This form of concrete was used as far back as Roman times. Roman engineers used it to build the huge dome of the Pantheon and as construction material for many aqueducts.

It is also used as an abrasive, especially in polishes, pencil eresers, cosmetic exfoiants and the production of stone-washed jeans. "Pumice stones" are often used in beauty salons during the peducure process to remove dry and excess skin from the bottom of the foot as well as calluses. It was also used in ancient Greek and Roman times to remove excess hair.Finely ground pumice is added to some toothpastes and heavy-duty hand cleaners (such as lava soap) as a mild abrasive. Pumice is also used as a growing substrate for growing horticultural crops. Some brands of chinchilla dust bath are made of powdered pumice.

Owing to its high demand particularly for water filtration, chemical spill containment, cement manufacturing, horticulture and increasingly for the pet industry, mining of pumice in environmentally sensitive areas have 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 Winlderness.