| Lat / long: | 38.38325, -118.75957 |
| Primary: | Gold |
| Secondary: | Silver |
| Tertiary: | Zinc, Copper, Nickel |
| Ore: | Gold, Cinnabar, Chalcopyrite, Chalcocite, Sphalerite, Covellite, Tetrahedrite, Tennantite, Enargite, Matildite, Nagyagite, Niccolite, Alunite, Feldspar, Barite, Pyrite, Hematite, Montmorillonite, Kaolinite, Marcasite, Arsenopyrite, Pyrrhotite |
| Gangue: | Quartz |
| Orebody form: | tabular to irregular |
| Discovery year: | 1930 |
| Operation type: | Surface-Underground |
| Deposit type: | volcanic-hosted disseminated |
| Production size: | Medium |
| Development status: | Producer |
| Production years: | 1981-1990 |
| First production started: | 1981 |
| Last production ended: | 1990 |
| Host type: | Andesite,Tuff,Volcanic Breccia (Agglomerate) |
| Structure: | Major regional structural trends affecting the mine area are the Walker Lane shear zone and the Borealis Trend., NE-trending faults with subordinate N-S and E-W- striking structures. |
| Alteration processes: | Host rock alteration consists mainly of pervasive silicification, alunitization, kaolinization, oxidation, argillization, and propylitization. The conduit for hydrothermal fluids was a 100-200 ft. wide core zone of silica breccia with abundant iron oxide minerals. The silica breccia zone narrows downward and grades downward into oxidized quartz-sulfide and unoxidized quartz-pyrite alteration. Argillic and propylitic alteration zones develop outward from core. Barren opal and chalcedonic silica overlie deposit. |
| MRDS | M035782 |
| DEP | 10310350 |
| Reference | {Deposit:: Reid, R. F., Jr., 1984, The geology of the Borealis deposit: GSA Abstracts with Programs, 97th Ann. Mtg, Reno, NV.}{Deposit:: NBMG Mining District File 200, Items 8, 9, Press Clippings.}{Deposit:: Tooker, E.W., 19?, In USGS Bull 1646.}{Deposit:: Strachan, D.G., 19?, Geologic Discussion of the Borealis Gold Deposit, Mineral Co., Nevada, in USGS Bull 1646.}{Deposit:: Bulk-Mineable Precious Metals Symposium, 1987, Field Trip Guidebook.}{Deposit:: NBMG, 1994, MI-1993}{Deposit:: Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Database of significant deposits of gold, silver, copper, lead, and zinc in the United States; Part A, Database description and analysis; part B, Digital database: U.S. Geological Survey Open-File Report 98-206, 33 p., one 3.5 inch diskette.}{Deposit:: Golden Phoenix Co. website, 2006.}{Deposit:: Gryphon Gold website, 2006.}{Deposit:: Struhsacker, Eric, guidebook editor, 1994, Geological Society of Nevada Special Publication #20, Gold Deposits of the Central Walker Lane, Nevada: mineralization Style and Mine Closure Planning.}{Deposit:: Eng, T., 1991, Geology and Mineralization of the Freedom Flats Gold Deposit, Borealis Mine, Mineral County, in Raines and others, Geology and Ore Deposits of the Great Basin, Symposium Proceedings, Reno, NV: Geological Society of Nevada, v. 2, p. 995-1019.} |
| Reporter | LaPointe, D.D., Schruben, Paul G. |