[Answer] Which is the only rock that can float in water?

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Which is the only rock that can float in water?

• pumice:Everyone knows from elementary science classes that rocks are usually denser than water and therefore sink. It is the difference between the density of the water and the density of the rock that makes it impossible for the rock to maintain buoyancy and float. There is a volcanic rock, called pumice, that can defy this common knowledge, however. Pumice is the only rock that can float in water. Pumice forms when lava and water mix, causing a rapid change in the pressure inside the material. Gases dissolve in to the lava as it hardens. This leaves small air pockets in the pumice's structure, which allow it to float. Source: Sciencing.com

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