Perlite

Commercial perlite is a glassy rock which will expand to between three and thirty-five times its original volume when rapidly heated in a suitable furnace. Perlite resources in the United Kingdom are confined to Sandy Braes, Northern Ireland, but glassy rocks in Scotland may prove to be sources of perlite. Expanded perlite is used as a thermal and acoustic insulator, filter aid, filler, carrier or horticultural aggregate. The largest use for expanded perlite in the United Kingdom is as a lightweight aggregate in plasters. Crude perlite is used in the foundry and steel industries. World production of crude perlite is about two million tonnes annually. The United Kingdom imports about 115,000 tonnes of crude perlite annually, mainly from Greece and Italy. The largest consumers in the United Kingdom are British Gypsum Limited and Tilcon Limited, both of which produce lightweight plasters. Filter aid production is dominated by Johns-Manville (G.B.) Limited and The British CECA Company Limited. Steetley Minerals Limited import Dicalite filter aids from Belgium.