Mining was Norway's oldest major export industry—some working mines were established more than 300 years ago—and, for a time, silver, iron, and copper were important exports. Iron pyrites and iron ore were still mined in considerable quantities. Petroleum and gas comprised Norway's leading industry in 2002, and metals, chemicals, and mining were among other leading industries. Among export commodities, petroleum and petroleum products ranked first—Norway was vying with Russia to be the second-largest exporter of oil—while metals and chemicals followed close behind. Known deposits of other minerals were small; they included limestone, quartz, dolomite, feldspar, and slate. In 2001, production of iron ore and concentrate (metal content) was 340,000 tons, down from 462,000 in 1997; titanium (metal content) production was 265,000 tons. Norway also produced nickel, hydraulic cement, dolomite, feldspar, graphite, lime (hydrated, quicklime), limestone, flake mica, nepheline syenite, nitrogen, olivine sand, quartz, quartzite, soapstone, steatite, sulfur (as a byproduct), and talc. No lead or zinc was mined in 1998–2001, and no copper or pyrite in 1999–2001. The largest titanium deposit in Europe was at Soknedal. A large plant at Thamshavn used half the Orkla mines' output of pyrites for sulfur production. Reserves of minerals generally have been depleted, except for olivine, which was abundant. There has been recent gold exploration, and a zinc exploration program in the Roros district confirmed the existence of extensive stratiform sulfide mineralization with dimensions of a type that could host commercial deposits.