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This classic site operated as a copper-lead-zinc-silver-and more site for more than a century, and it has produced specimens that dot museums and private collections worldwide. The mineralization formed in a pipe that cross-cuts a series of metamorphosed, late Precambrian aged sedimentary rocks. The pipe is thought to be a sedimentary beccia, formed when fluids dissolved a pathway through the surrounding limestones and overlying sediments collapsed downwards to fill that path. The vertical pipe allowed fluids to concentrate various metal elements inside the pipe, and the presence of oxygen at the surface allowed minerals to dissolve there and be concentrated again at depth. Cuprite forms from these sorts of redox processes involving copper – it is most soluble near the surface with ample oxygen, then precipitates back out of solution when the copper is reduced at depth. -JBB Image credit: Rob Lavinsky/Irocks.com (standing permission) https://www.irocks.com/minerals/specimen/48258 #Mineralmonday Reference: http://www.tsumeb.com/en/geology/