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Instructions
Observe the weight. Pumice is porous and so light it will float on water when dry. Eventually, however, water will seep into the pores and it will sink.
Look at the color. Rhyolite and trachyte pumices are generally white due to the high silica content and low iron and magnesium content. Andesite pumices are frequently brown or yellow while the more rare basalt pumices are black.
Examine the microscopic structure. It is a glass pyroclastic composed of micro-vesicles elongated, rounded or tubular depending on the manner in which the lava was flowing when it solidified. The glass forms fibers and threads between the vesicles.
Study the composition. It contains small crystals of many different minerals including augite, feldspar, hornblende and zircon. Older pumice becomes filled with other minerals introduced by water.
Find pumice in young volcanic fields. It is unstable and fractures easily due to its high porosity which averages 90 percent. Pumice can be found in many countries, but the largest producer is Italy. Other major producers include Chile, Greece, Spain, Turkey and the United States.