Mining in Brazil is centered on the extraction of iron (the second largest global iron ore exporter), copper, gold, aluminum (bauxite-one of the 5 biggest world's productors), manganese (one of the 5 biggest world's productors), tin (one of the biggest world's productors), niobium (concentrates 98% of the known niobium reserves in the world), and nickel. About gemstones, Brazil is the world's largest producer of amethyst, topaz, agate and is a big producer of tourmaline, emerald, aquamarine, garnet and opal.