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| It is considered a ] 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 ]. It is widely used to make lightweight ] and as an ], especially in polishes and ] exfoliants. | It is considered a ] 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 ]. It is widely used to make lightweight ] and as an ], especially in polishes and ] exfoliants. | ||
| When used as an additive for cement, 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 cement, 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. | ||
Revision as of 23:48, 9 October 2004
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.
on Tenerife, Canary Islands. Density of specimen
approx 0.25 g/cm³. Scale in centimetres.
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 cosmetic exfoliants.
When used as an additive for cement, 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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