Porcellanite


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porcellanite

[pȯr′sel·ə‚nīt]
(petrology)
A hard, dense siliceous rock, such as impure chert or indurated clay or shale.

Porcellanite

 

clays, argillaceous schists, clay marls, and other rocks altered through the action of underground fires in coal seams into dense, porcelaneous rocks, which may be white, pink, mottled, or dark. Porcellanite also contains mullite, cordierite, wollastonite, and other minerals. It is formed at temperatures reaching 1,300°C. Porcellanite is also formed when waste piles burn and sometimes assumes a slaglike appearance.

Porcellanite is used as a building material, namely ballast; when pulverized, it acquires binding properties and is used as a cement additive. In the USSR, it is mined in the Angren River valley in Uzbekistan, where kaolin clays between coal seams have been altered. The term “porcellanite” is common in the United States, where it is applied to an impure variety of a siliceous rock, usually opalescent, that has the texture and luster of unglazed porcelain.

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7 earth Site Stone Environmental artefacts context HI2 hinterland margin adjacent to saltflats HI6 porcellanite flakes inland HI66 tuff flake hinterland margin adjacent to swamp HI80 saltflats HI81 quartz flakes hinterland margin adjacent to saltflats HI83 quartz flakes inland quartzite pestle HI97 quartz flakes hinterland quartzite mortar margin adjacent to saltflats
Other cultural material observed includes charcoal, bone and the very occasional stone artefact, except in site HI6, which contained numerous flakes throughout the deposit, manufactured from porcellanite, as well as white ochre.
The excavations revealed a low density of stone artefacts in all but the earth mound site (HI6), which contained only unspecialised flakes manufactured from a locally occurring porcellanite.