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Pumice

Pumice is a highly vesicular pyroclastic igneous rock of intermediate to siliceous magmas including rhyolite, trachyte and phonolite.

Pumice is usually light in colour ranging from white, yellowish, gray, gray brown, and a dull red.

Pumice has an average porosity of 90%.

Pumice is formed as pyroclastic material is ejected into the air as a froth containing masses of gas bubbles or vessicles, the lava solidifies quickly and the vessicles are contained in the rock.

Note:   The above text is excerpted from the Wikipedia article "Pumice", which has been released under the GNU Free Documentation License.
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May 27, 2017

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