U.S. Geological Survey Circular

1998 mean estimate 1998 National Mineral Adirondack Mountains Alaska Peninsula Appalachian Mountains areas Basin and Range Berger Briskey Brobst Brooks Range Byron Church Dennis Cox Michael data base David deposit model type Diggles discoveries East-central economic exploration EXTENSIONS TO IDENTIFIED GEOLOGICAL SURVEY 1998 Geological Survey Professional grade and tonnage Gregory hypothetical resources identified resources James Jeanine Keith Gregory kilotons lead resources Lindsey major deposit types massive sulfide deposits metal Michael F mineral deposit model Mineral Resource Assessment mining National Mineral Resource Northern Appalachian number of undiscovered past production porphyry copper deposits Pratt Professional Paper 820 Region Teams—Continued RESOURCE ASSESSMENT TEAM Rytuba Michael G Sandra H.B. Clark sedimentary exhalative deposits Significant Deposits significant mineral deposits silver Singer Southern Basin Spanski Steve Ludington submodel Survey Professional Paper Thomas Nash tonnage models U.S. Geological Survey undiscovered deposits undiscovered resources United States mineral USGS Western United world reserves Zientek zinc in undiscovered