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| When used as an additive for ], a fine-grained version of pumice called ] is mixed with ] to form a light-weight, smooth, plaster-like ]. This form of concrete was used as far back as ] times. | When used as an additive for ], a fine-grained version of pumice called ] is mixed with ] to form a light-weight, smooth, plaster-like ]. This form of concrete was used as far back as ] times. | ||
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| An ancient ] ] for strong ] | |||
| *Chewing on soft pumice till ‘''] like''‘ filled small holes safely | |||
| *Sucking the pumice stone before chewing extracted ], and other ] that were digestable for humans. | |||
| '''''PLEASE NOTE''''' Pumice should '''NOT''' be swallowed. Although, some have taken to ]. ''It is not advised.'' | |||
| : ] 11:42, 5 September 2005 (UTC) | |||
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| {{mineral-stub}} | {{mineral-stub}} | ||
Revision as of 10:54, 11 September 2005
Pumice is a light, porous type of pyroclastic igneous rock. It is formed during explosive volcanic eruptions when liquid lava is ejected into the air as a froth containing masses of gas bubbles. As the lava solidifies, the bubbles are frozen into the rock. Any type of igneous rock — andesite, basalt, dacite or rhyolite — can form pumice given suitable eruptive conditions. When larger amounts of gas are present, the result is a finer-grained variety of pumice known as pumicite.
It is considered a glass because it has no crystal structure. Pumice varies in density according to the thickness of the solid material between the bubbles; many samples float in water. It is widely used to make lightweight concrete and as an abrasive, especially in polishes and cosmetics exfoliants.
When used as an additive for cement, a fine-grained version of pumice called pozzolan is mixed with lime to form a light-weight, smooth, plaster-like concrete. This form of concrete was used as far back as Roman times.
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