Pinal County. The Mammon Mine near the western side of the Slate Mountains is about 30 miles from Casa Grande. It has yielded a little high-grade ore. The Casa Grande district included the Silver Reef in southwestern Pinal County, where free gold has been found in veins at the Mammon Mine, and probably, occurred in other parts of the range. North Carolina. In 1799, a boy named Conrad Reed found a 17-pound hunk of gold on his family’s farm in Cabarrus County, North Carolina.. A new online inventory that catalogues abandoned and orphaned mines across Canada is now available to the public.. The inventory, released in April, is a project of the National Orphaned and Abandoned Mines Initiative (NOAMI). NOAMI was launched in 2002 in response to a request from mine ministers in federal, provincial and territorial jurisdictions to address issues related to orphaned and. Finding an abandoned gold mine available for panning requires prior research on which tracts of land are fair game and which aren't up for grabs. The U.S. Department of the Interior's Bureau of.