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
Galena, Illinois Galena, Illinois Galena is the largest city in and the county seat of Jo Daviess County, Illinois, with a population of 3,429 at the 2010 census. A section of the city is listed on the National Register of Historic Places as the Galena Historic District. The city is named for the mineral galena, which was mined by Native Americans in the area for over a thousand years. Owing to these deposits, Galena was the site of the first major mineral rush in the United States. By 1828, the population was estimated at 10,000, rivaling the population of Chicago at the