Feb 15 (Reuters) - Martial law in Guinea has forced the world's biggest bauxite exporter, Compagnie des Bauxites de Guinee (CBG), to halt mining activities and deliveries of ore to the Kamsar port, company officials have said. Guinea, which holds a third of the world's bauxite reserves, has been gripped by a wave of violent protests against President Lansana Conte's 23-year rule. Here are some key facts about world bauxite production and reserves: * OVERVIEW: -- Bauxite is the ore from which aluminium is produced. It is refined to produce alumina, which is further processed to make aluminium. -- Deposits are found near the earth's surface with an average thickness of 4-6 metres. Bauxite is usually mined in open pits. * PRODUCTION AND RESERVES: -- Guinea has the world's largest bauxite reserves and is the biggest exporter of the ore while Australia tops the world in mine production. -- The Huntly mine in Australia, owned by Alcoa World Alumina, is the world's largest, producing 18 million tonnes in 2006. * TOP 5 PRODUCERS IN 2006: Country Quantity (In millions of tonnes) 1. Australia 61.4 2. Brazil 21.0 3. China 20.0 4. Greece 15.2 5. Jamaica 14.9 Total incl. Others 177.0 - - - - - - - - - - - - * RESERVES (Top five): Country Reserve Base (In billions of tonnes) 1. Guinea 8.6 2. Australia 7.9 3. Brazil 2.5 3. Jamaica 2.5 5. China 2.3 Total incl. Others 32.0 - - - - - - - - - - - - * WORLD'S FIVE BIGGEST MINES: Country Company Plant name Capacity Production (Millions of tonnes) (2006) 1. Australia Alcoa World Huntly 18.0 18.0 Alumina 2. Guinea Compagnie des Boke 15.0 14.0 Bauxites de Guinee (CBG) 3. Brazil Mineracao Rio Trombetas 16.3 17.8 do Norte (MRN) 4. Australia Rio Tinto Weipa 15.5 16.1 5. Australia Worsley Alumina Mt Saddleback 10.0 10.0 Sources: Reuters; International Aluminium Institute (www.world-aluminium.org); U.S. Geological Survey (www.usgs.gov)
