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
Ore shoot Ore shoot In mining and geology, an ore shoot is a long seam of mineral or metal bearing rock that can be profitable to extract. The term may have originated in the 17th and 18th centuries when various theories existed on the origins of ore deposits, including some that suggested they grew like trees. Tabular or sheet-like deposits of metalliferous ores often contain areas of enhanced metal content that are larger in one dimension than another. A structure may contain multiple ore shoots. A "vein," "lode" or other mineral-bearing structure could be thick, steeply inclined within the host rock, persisting