Cambodia's mineral resources, though limited, had not been extensively explored and developed in the past two decades because of war, internal conflict, and the lack of appropriate legislation and policy to attract foreign investors. The mining sector, the smallest in the economy, contributed 0.16% to the country's GDP in 2001 and employed 4,000 people in 2000. In 2001, the country produced modest quantities of clinker cement, laterite blocks, phosphate rock, quartz sand, sand and gravel, crushed stones, sandstone, and salt; clay, gemstones, gold, iron ore, and lime were presumably produced as well. Cement and gem mining were leading industries in 2002. Other metallic minerals identified in the country were antimony, bauxite, chromium, copper, lead, manganese, molybdenum, silver, tin, tungsten, and zinc. In addition, Cambodia had resources of such industrial minerals as carbonate rocks, fluorite, quartz, silica sand, and sulfur. Iron deposits and traces of gold, coal, copper, and manganese have been reported in the Kampong Thum area. Substantial deposits of bauxite, discovered in the early 1960s north of Battambang and southeast of Phnom Penh, have yet to be worked. Potter's clay was common, and deposits of phosphates, used for fertilizer, existed in southern Kampot province and near Phnom Sampou. Precious gems were mined in the Pailin area and smuggled to Thailand. High-quality cornflower-blue sapphires have been the most valued gemstone produced to date, and high-quality rubies also have been found. It was unlikely that exploitation of the nation's mineral resources could be undertaken without continued removal of landmines.