Ore genesis accumulation of hematite gravels called "pisolites" which form channel-iron deposits. These are preferred because they are cheap to mine. Lead-zinc deposits are generally accompanied by silver, hosted within the lead sulfide mineral galena or within the zinc sulfide mineral sphalerite. Lead and zinc deposits are formed by discharge of deep sedimentary brine onto the sea floor (termed "sedimentary exhalative" or SEDEX), or by replacement of limestone, in skarn deposits, some associated with submarine volcanoes (called volcanogenic massive sulfide ore deposits or VMS), or in the aureole of subvolcanic intrusions of granite. The vast majority of SEDEX lead and zinc deposits
Mineral industry of Colombia Mineral industry of Colombia Mineral industry of Colombia refers to the extraction of valuable minerals or other geological materials in Colombia. Colombia is well-endowed with minerals and energy resources. It has the largest coal reserves in Latin America, and is second to Brazil in hydroelectric potential. Estimates of petroleum reserves in 1995 were . Colombia also possesses significant amounts of nickel and gold. Other important metals included platinum and silver, which were extracted in much smaller quantities. Colombia also produces copper, small amounts of iron ore, and bauxite. Nonmetallic mined minerals include salt, limestone, sulfur, gypsum, dolomite, barite, feldspar, clay,