Sri Lanka's major mineral commodities were graphite and colored gemstones. However, 18 years of civil war, prolonged drought, high oil prices, and an electricity crisis have crippled its economy—GDP declined by 1.3% in 2001, its lowest level in a decade. Graphite production, which was controlled by the government, totaled 6,585 tons in 2001, up from 5,902 in 2000. The island's gem industry was world famous. In the Ratnapura district, there were considerable deposits of sapphire, star sapphire, ruby, star ruby, cats eye, chrysoberyl, beryl, topaz, spinel, garnet, zircon, tourmaline, quartz, and moonstone. A lapidary industry was established for the international marketing of cut and polished precious and semiprecious gemstones. No ouput figures were available for 2001, but in 2000, 380,500 carats of star sapphire, 173,700 carats of saffire, and 6.5 million carats of other precious and semiprecious gemstones other than diamond were produced, half that of 1999. Large quantities of kaolin and apatite have been found, and there were large surface deposits of quartz sand—kaolin and quartz sand were mined. Limestone dating from the Miocene era was quarried from the Jaffna peninsula and used in the manufacture of cement. In the dry-zone coastal areas, salt was manufactured by solar evaporation of seawater. In addition, Sri Lanka produced clays (brick, tile, and for cement production), feldspar, and phosphate rock, and presumably produced varieties of stone and sand and gravel. Cement production and petroleum refining were among the country's leading industries in 2002, and diamonds ranked third among export commodities; petroleum products ranked fifth. The beach sands contained large quantities of ilmenite, rutile, monazite, and zircon, although none was produced in 1999–2001; in 1998, 84,118 tons of ilmenite concentrate was produced, 1,930 of rutile, and 8,814 of zircon. There were plans to revive mineral sands operations, including of garnet sands discovered along the southern coastline. Although no rare earth metals were produced in 2000–2001, the cerium, yttrium, zirconium, niobium, tantalum, thorium, and uranium groups have been found, and thorianite appeared to be widely distributed.