Quarrying for limestone and other building materials was the major mining activity in Malawi, but gemstones, including agate, amethyst, aquamarine, garnet, rhodolite, rubies, and sapphires, have also been produced, on a small scale. In 2000, 183,000 tons of limestone was quarried for the manufacture of cement, which was Malawi's fifth leading industry in 2002. About 665 kg of gemstones were extracted in 2000, down from 934 in 1998; gemstones accounted for 95% of the nearly $1 million in mineral exports in 1999. Also produced were dolomite, lime, artisanal salt, and crushed stone for aggregate, as well as possibly clays, sand and gravel, and other stone. The country had known deposits of apatite, asbestos, bauxite, columbium (niobium), corundum, dimension stone (including blue and black granite), galena, gold, granite, graphite, ilmenite, kaolin, kyanite, mica, monazite, phosphate rock, pyrite, rutile, tourmaline, uranium, and vermiculite, which have occasionally been exploited. Prospecting for other minerals has been undertaken, but no resources of commercial significance have been discovered, except for coal, bauxite (28.8 million tons), kaolin (14.1 million tons), silica sand (25 million tons), and monazite and strontianite (11 million tons in Kangankunde Hill). Mining and quarrying accounted for 1% of GDP in 1999, and has grown sharply since 1995 because of higher output of aggregates, cement, and coal. No minerals were among the leading export commodities. The outlook for Malawi's mineral industry was tied to the country's ability to spur exports, improve educational and health facilities, solve environmental problems of deforestation and erosion, and deal with the rapidly growing problem of HIV/AIDS.