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| ], below that is pumice and in lower right hand color is ] (light color).]] | ], below that is pumice and in lower right hand color is ] (light color).]] | ||
| '''Pumice''' is a light, porous type of ] ]. It is formed during explosive ] eruptions when liquid ] 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 |
'''Pumice''' is a light, porous type of ] ]. It is formed during explosive ] eruptions when liquid ] 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 — ], ], ] or ] — can form pumice given suitable eruptive conditions. | ||
| <div style="float:left;margin-right:0.5em;text-align:center"> | <div style="float:left;margin-right:0.5em;text-align:center"> | ||
| ]<br> | ]<br> | ||
| <small>''Specimen of highly porous pumice from ] volcano <br>on ], ]. Density of specimen <br>approx 0.25 ]/]. Scale in ]s.''</small></div> | <small>''Specimen of highly porous pumice from ] volcano <br>on ], ]. Density of specimen <br>approx 0.25 ]/]. Scale in ]s.''</small></div> | ||
| 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. | ||
Revision as of 14:24, 10 September 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.
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