Pumice is a type of rock, according to the Mineral Information Institue, that is formed when lava with a very high water or gas content is ejected from a volcano. As the gases escape, tiny bubbles form within the lava, making it frothy. As the lava cools, these bubbles are trapped, forming a foam made of solid rock. In fact, the name pumice is derived from the Latin word "pumex" which means "foam."
Description
Usually light to dark gray in color, pumice generally has a very rough and abrasive quality and can feel somewhat sandy at times. The texture of pumice can range from very coarse with large and visible bubbles within the rock, to very fine with almost microscopic bubbles. Due to its airy consistency, it is extremely light and is the only rock that will float on water.
Properties
Pumice consists primarily of rock that is high in silica, and low in iron or magnesium, and is often classified as a type of rock called rhyolite. Pumice is often found near deposits of obsidian, the form of volcanic glass that is also high in silica. It is a relatively soft rock and erodes more quickly that other volcanic rocks.
Sources
Exclusively found in areas of volcanic activity, pumice is collected in more than 50 countries around the world. The largest producer of pumice is Italy. Greece, Chile, Turkey and Spain also produce pumice. In the United States, pumice is most commonly quarried in Arizona, New Mexico, California and Oregon.
Commercial Uses
Commercially, pumice is used in the manufacture of lightweight construction materials including concrete and concrete block. Pumice is also used in abrasives, plasters and finishes, cleaning products, paints, filtration systems,and in agriculture as a soil conditioner. Large pumice boulders are often used as accent pieces in landscaping, because they are easy to transport, shape and position.
Home Uses
Pumice is a primary ingredient in the soap Lava, which uses ground pumice as an abrasive to clean. Ground pumice is also used in other products as a skin scrub. Pumice rocks are frequently used as heating elements in charcoal grills and fire pits. Pumice stones are often cut into small pieces and finished with a flat surface. These stones are intended for scrubbing and removing calloused skin that has been softened by soaking in warm water.
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