Ecuador was heavily dependent on petroleum production, its leading industry and export commodity in 2002. The country had extensive but underdeveloped gold resources and other minerals. In 2001, Ecuador produced cadmium, copper, gold, lead, silver, zinc, cement, bentonite, common clay, kaolin, feldspar, crude gypsum, silica (glass sand), ferruginous sand, stone, sand and gravel (limestone, marble, pozzolan, pumice), salt, and sulfur. The country also contained known mineral resources of bismuth and tin. Production totals for 2000 included gold, 2,823 kg, down from 7,208 in 1996; silver, 2,000 kg, up from 1,325 in 1996; kaolin, 11,022 tons, down from 86,541 in 1996; limestone (for cement manufacture), 3.15 million tons, down from 4.2 million tons in 1998; and marble, 1,679 tons, down from 17,225 in 1996. The slow pace of exploration and mining activities reflected low metal prices and recent political and economic uncertainties and disappointments.