What Type of Rock Is Pumice?

Classification

• Pumice is classified as an extrusive igneous rock. Igneous rocks are the products of solidified magma. The "extrusive" classification indicates that pumice cools on the earth's surface rather than underground. Pumice lacks a crystalline structure, resulting in its classification as a glass.

Texture

• The magma that eventually forms pumice contains trapped gas and the cooling action that occurs after the magma erupts from a volcano allows this gas to escape. A network of holes forms within the pumice as a result.

Location

• Italy provides the largest amount of pumice for commercial use and pumice is also found extensively in Greece, Chile, Spain, Turkey and the United States. California, Arizona, New Mexico and Oregon hold America's greatest pumice concentrations.

Commercial Uses

• In commercial parlance, pumice refers to large, intact stones while pumicite refers to fine particles of pumice. According to the Mineral Information Institute, approximately 75 percent of pumice consumption goes into concrete manufacture. Pumicite is also a common ingredient in soaps and cleansers.