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What Is Pumice Composed of?

The Mineral Information Institute describes pumice as a volcanic rock formed when lava with a high content of water and gases is thrown out of a volcano. Escaping gas bubbles cause the lava to become frothy, with the bubbles giving pumice its characteristic porous texture as it cools.

Composition
- Igneous rocks, including pumice, are formed when molten volcanic material cools and hardens. The National Park Service says that volcanic rock is classified according to its silicon content, with rhyolites and dacites having high levels of silicon and andecites and basalts having less silicon. Pumice forms most often from high-silicon material and generally has low iron and magnesium content as well.
Characteristics
- Pumice is often light in color due to its high silicon content. Being porous, it is very lightweight and will float until the open cells fill with water. The United States Geological Survey says that in the aftermath of volcanic eruption, blocks of pumice have been observed floating in the ocean.
Uses
- Pumice may be used as an abrasive tool for skin care.
  
  Pumice is often used as a building materials because it is strong and lightweight. According to the Mineral Information Institute, about three-quarters of the pumice mined commercially is utilized this way. Other uses include commercial abrasives, landscaping materials and the creation of stone-washed blue jeans.

Rocks & Minerals