U.S. Geological Survey Circular, Issue 1178

1998 mean estimate 1998 National Mineral 90-percent probability Adirondack Mountains Appalachian Mountains areas Basin and Range Briskey Brobst Brooks Range chalcopyrite Church Dennis contained in undiscovered copper resources Cox Michael data base deposit model type discoveries East-central economic epithermal vein felsic grade and tonnage Gregory hypothetical resources identified resources Inferred reserves kilotons lead resources major deposit types massive sulfide deposits mineral deposit model Mineral Resource Assessment mining National Mineral Resource NM NM NM number of undiscovered past production permissive tracts plutonic porphyry gold porphyry copper deposits Pratt Professional Paper 820 Region Teams-Continued reserve base resource was estimated rocks Rytuba Michael Sandra H.B. Clark sediment-hosted copper sedimentary exhalative sedimentary exhalative deposits Significant Deposits significant mineral deposits silver skarn Spanski sphalerite Steve Ludington stockwork stockwork veinlets submodel sulfosalts Survey Professional Paper Thomas Nash tonnage models total discovered U.S. Geological Survey undiscovered deposits undiscovered mineral deposits undiscovered resources USGS zinc zinc in undiscovered