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Getchell Mine (North Pit; Center pit; South pit), Adam Peak, Potosi District, Osgood Mts, Humboldt Co., Nevada, USA
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Latitude: 41°12'58"N
Longitude: 117°15'24"W
 
 
A former Au-Ag-As-W-Sb-Hg-Ba(baryte)-Mo-F-Tl-Te-Bi-Sn-Pb-Zn-Cu mine located in secs. 4 & 9, T38N, R42E, and in secs. 28, 29, 32 & 33, T39N, R42E, MDM, 7.4 km (4.6 miles) NNE of Adam Peak (coordinates of record), on private land within a Bureau of Land Management administered area. Discovered by Edward Knight and Emmet Chase in 1933. Overall life of the mine is 1938-present. Owned & operated by the First Miss Gold Corp. Owned & operated by Newmont Gold Mining Company (2003) & Placer Dome Gold (2003). Operated during the periods 1938-1945, 1948-1950, 1962-1967, 1985-1999. MRDS database stated accuracy for this location is 10 meters.

The Getchell property consists of the Getchell, Turquoise Ridge and N Zone deposits. The Main pit has now encompassed the earlier Central and South pits. This is the same location as the old MRDS record M055410.

Prospectors Edward Knight and Emmet Chase discovered gold in 1933 and located the first claims in 1934. With the financial backing of Noble Getchell and George Wingfield, the Getchell Mine, Inc. was organized in 1936 and was brought into production in 1938. In 1938, the mining rate was about 500 tons per day of oxide ore and 150 tons per day of sulfide ore. Sulfide ore was roasted at 1500 degrees Fahrenheit for one hour and fifteen minutes preparatory to cyanidization. In 1941, a Cottrell electric precipitating unit was installed to save the arsenic that was liberated by roasting the sulfide ore, and in 1943-1945, when government wartime restrictions forced the shutdown of many gold producers, Getchell mine was permitted to continue operations as a producer of "strategic" arsenic. In 1943, arsenious oxide was being produced at the rate of 10-25 tons per day from furnace fume. Also in 1942, a 227 tonne scheelite flotation plant was built to recover tungsten from Getchell ore. A slack labor supply, and high supply costs forced the gold operations to cease at the end of World War II. The US Bureau of Mines developed a carbon recovery process on site and the mine reopened in 1948 with expanded mill capacity and more underground development, but closed again in mid-1950 when known oxide reserves were exhausted. Gold production was suspended in 1951. From 1951-56, the mill processed tungsten ores mined from throughout the district. Tungsten production ceased in 1957. in 1960, Goldfield Consolidated Mines Co. purchased the interests in Getchell Mine, Inc. from the estates of Wingfield and Getchell. Gold production resumed in June 1962 and continued to December, 1967, when the mine was closed and the mill dismantled. Cyprus Mines formed a joint venture with Goldfield in 1970, with Cyprus as operator. Cyprus dropped the property at the end of 1971. Conoco leased the property from Goldfield in 1972 and completed exploration including over 300 drill holes. Metallurgically difficult sulfide reserves were identified during this program. Conoco subleased the property from 1975 to 1978 to General Electric Co. who conducted tungsten exploration along the margins of the Osgood Stock. In 1981, Conoco purchased the property from Goldfield Corp., but by 1983 had sold the property to First Mississippi for $5 million. At that time the property consisted of 14,100 acres of fee land and almost 5000 acres of unpatented claims, and reserves at the time of purchase were in excess of 750,000 ounces of gold. Mining feasibility and metallurgical studies were initiated in 1984. Heap leaching of waste rock dumps from previous mining operations commenced at the end of fiscal 1985, producing 91 ounces of gold in that fiscal year. By mid-1985, the Getchell property had increased the area of unpatented claims to 13,900 acres. In May, 1987, the board of First Mississippi Corp. authorized open pit mine development and construction of a new mill utilizing autoclave technology to process 3000 tons of ore per day. The mill was completed and production resumed in 1989 combining a traditional cyanide leach circuit with pressure oxidation. The mill started up on oxide ore in February, 1989. Sulfide ore was run through the first pressure oxidation autoclave in April, 1989 followed by the start up of the other two autoclaves in May and June, 1989. By the end of fiscal year 1989, project capital costs stood at $90.3 million, 14% over the June 1987 feasibility study estimate. In fiscal year 1989, overall gold recovery for combined oxide and sulfide mill ores was 89.8%. Heap leaching of waste rock from previous mining operations was completed in fiscal year 1989. Heap leaching continued beyond this date using oxide reserves from the Summer Camp orebody discovered in 1985.

Production of oxide open pit ore commenced at the nearby Turquoise Ridge mine in 1991 and in the same year, an underground orebody adjacent to the pit area. This ore was to be mined when the pit level was deep enough to provide lateral access. In 1995, First Miss Gold changed its name to Getchell Gold. Underground production commenced at Turquoise Ridge Mine in May 1998. On May 27, 1999 Placer Dome completed a merger with Getchell Gold Corporation, resulting in Placer Dome owning 100% of the Getchell gold property. Gold production has been suspended since July 1999 and the property is on care and maintenance. Production from approximately 58% of the property is subject to a 2% net smelter return royalty payable to Franco Nevada Mining Corporation Ltd. Placer Dome wrote off the carrying value of the property in 2001. On October 25, 2001, Newmont Mining Corporation and Getchell Gold Corporation signed a letter of intent under which Newmont would buy ore from the Getchell mine for processing at Newmont's adjacent Twin Creeks mine.Production of oxide open pit ore commenced at the nearby Turquoise Ridge mine in 1991 and in the same year, an underground orebody adjacent to the pit area. This ore was to be mined when the pit level was deep enough to provide lateral access. In 1995, FirstMiss Gold changed its name to Getchell Gold. Underground production commenced at Turquoise Ridge Mine in May 1998. On May 27, 1999 Placer Dome completed a merger with Getchell Gold Corporation, resulting in Placer Dome owning 100% of the Getchell gold property. Gold production has been suspended since July 1999 and the property is on care and maintenance. Production from approximately 58% of the property is subject to a 2% net smelter return royalty payable to Franco Nevada Mining Corporation Ltd. Placer Dome wrote off the carrying value of the property in 2001. On October 25, 2001, Newmont Mining Corporation and Getchell Gold Corporation signed a letter of intent under which Newmont would buy ore from the Getchell mine for processing at Newmont's adjacent Twin Creeks mine.

Mineralization is a polymetallic deposit (Mineral occurrence model information: Model code 173; USGS model code 26a.1; Deposit model name: Sediment-hosted Au; Mark3 model number 17), hosted in shale & limestone of the Preble Formation (Middle to Late Cambrian). The individual ore bodies are roughly tabular, strike NNW and dip 40-60E at a thickness of 1,000 meters, a width of 60.96 meters and a length of 2,133.6 meters. Controls for ore emplacement involved economic amounts of Au restricted to tabular, sheet-like zones (termed "veins" by Joralemon) within the Getchell fault zone and within favorable calcareous lithologies.

The known gold deposits within the Getchell Trend are Carlin- type, sediment-hosted, replacement deposits containing micron gold. Gold mineralization at Getchell is associated with a curvilinear fault system that strikes NNW and dips 40? to 75? east, on the eastern flank of the Cretaceous Osgood granodiorite stock. The mineralized fault zone and the Cretaceous granodiorite both cut Palaeozoic sediments of the Cambrian Preble and upper Cambrian to lower Ordovician Comus Formations which both belong to the Transition Assemblage, and the Ordovician Valmy Formation of the Western Assemblage. Thermal metamorphism along the intrusive contact formed tungsten bearing garnet-diopside skarns, passing outwards into wollastonite calc-silicates and marble. In the southern parts of the Getchell Mine area the skarn is about 30 m wide adjacent to the granodiorite contact, passing out into marble. Pelitic shales of the Preble and Comus Formations are thermally metamorphosed to cordierite-andalusite bearing hornfels nearest the contact, grading outwards into a biotite-cordierite-andalusite interval, to an outer biotite zone. The Osgood Stock and associated hornfels and skarns are found in both the footwall and hangingwall of the mineralized fault zones. Gold mineralization is found in a number of different rock types generally at the intersection of a number of high-angle and low-angle fault sets. The low-angle faults and associated folds are the result of Devonian and Permian-age compressional events and the higher angle faults and fracture sets formed during Tertiary extension. Mineralization is both structurally and stratigraphically controlled. Gold is associated with arsenic, mercury, and to a lesser extent antimony, and commonly with pervasive decalcification, silicification and carbonaceous alteration. Gold is micron-scale generally intergrown with arsenical pyrite, which in turn, is encrusted in barren, diagenetic pyrite. Late stage realgar and orpiment are commonly associated with high-grade ores. The main deposit is confined to a zone nearly 7000 ft. long at the northern end of the Getchell fault zone. Deep exploration shows that the mineralization persists at least 1 km down-dip on the Getchell fault system and also occurs along the parallel Village fault. Maximum width of ore is 200 ft., with an average width of 40 ft. Within ore zones, gold occurs as native grains that range in size from <1 micron to nearly 1 mm, with smaller grains more abundant than larger grains. Most of the gold is intimately associated with the fine grained quartz-carbon matrix of the altered rock termed "gumbo" by Joralemon (1951). Of the sulfides, pyrite and marcasite are principal hosts to gold. As of 1951, the gold:silver ratio in bullion ranged from 2:1 to 134:1 and averaged 10:1 for the entire bullion production to that date. Joralemon (1951) observed microscopic metallic grains in the Getchell ore that he concluded were native silver, although the particles were so small that conclusive chemical tests were not possible. No other silver minerals have been recognized except for very rare grains of electrum. Geochemical work at the Getchell mine and vicinity has demonstrated that As-W-Hg anomalies occur in rocks and soils over the arsenic-gold deposits and that these anomalies are not broad haloes but are restricted to the mineralized area. The highest metal contents are found in oxidized iron-rich material along fractures and bedding planes in barren bedrock, lesser values in caliche coatings on exposed bedrock, and lowest but still anomalous values in soil.The known gold deposits within the Getchell Trend are Carlin- type, sediment-hosted, replacement deposits containing micron gold. Gold mineralization at Getchell is associated with a curvilinear fault system that strikes NNW and dips 40? to 75? east, on the eastern flank of the Cretaceous Osgood granodiorite stock. The mineralized fault zone and the Cretaceous granodiorite both cut Palaeozoic sediments of the Cambrian Preble and upper Cambrian to lower Ordovician Comus Formations which both belong to the Transition Assemblage, and the Ordovician Valmy Formation of the Western Assemblage. Thermal metamorphism along the intrusive contact formed tungsten bearing garnet-diopside skarns, passing outwards into wollastonite calc-silicates and marble. In the southern parts of the Getchell Mine area the skarn is about 30 m wide adjacent to the granodiorite contact, passing out into marble. Pelitic shales of the Preble and Comus Formations are thermally metamorphosed to cordierite-andalusite bearing hornfels nearest the contact, grading outwards into a biotite-cordierite-andalusite interval, to an outer biotite zone. The Osgood Stock and associated hornfels and skarns are found in both the footwall and hangingwall of the mineralized fault zones. Gold mineralization is found in a number of different rock types generally at the intersection of a number of high-angle and low-angle fault sets. The low-angle faults and associated folds are the result of Devonian and Permian-age compressional events and the higher angle faults and fracture sets formed during Tertiary extension. Mineralization is both structurally and stratigraphically controlled. Gold is associated with arsenic, mercury, and to a lesser extent antimony, and commonly with pervasive decalcification, silicification and carbonaceous alteration. Gold is micron-scale generally intergrown with arsenical pyrite, which in turn, is encrusted in barren, diagenetic pyrite. Late stage realgar and orpiment are commonly associated with high-grade ores. The main deposit is confined to a zone nearly 7000 ft. long at the northern end of the Getchell fault zone. Deep exploration shows that the mineralization persists at least 1 km down-dip on the Getchell fault system and also occurs along the parallel Village fault. Maximum width of ore is 200 ft., with an average width of 40 ft. Within ore zones, gold occurs as native grains that range in size from <1 micron to nearly 1 mm, with smaller grains more abundant than larger grains. Most of the gold is intimately associated with the fine grained quartz-carbon matrix of the altered rock termed "gumbo" by Joralemon (1951). Of the sulfides, pyrite and marcasite are principal hosts to gold. As of 1951, the gold:silver ratio in bullion ranged from 2:1 to 134:1 and averaged 10:1 for the entire bullion production to that date. Joralemon (1951) observed microscopic metallic grains in the Getchell ore that he concluded were native silver, although the particles were so small that conclusive chemical tests were not possible. No other silver minerals have been recognized except for very rare grains of electrum. Geochemical work at the Getchell mine and vicinity has demonstrated that As-W-Hg anomalies occur in rocks and soils over the arsenic-gold deposits and that these anomalies are not broad haloes but are restricted to the mineralized area. The highest metal contents are found in oxidized iron-rich material along fractures and bedding planes in barren bedrock, lesser values in caliche coatings on exposed bedrock, and lowest but still anomalous values in soil.

Regional alteration: There is a metamorphic aureole around the Osgood Mountains granodiorite which has produced in the surrounding shaly rocks a mineral assemblage consisting of cordierite-, biotite-, and andalusite-hornfels. Locally limy beds are recrystallized and calc-silicate minerals are developed. Hydrothermal alteration consists chiefly of decarbonatization accompanied by silicification in the limestone beds. Cordierite, andalusite, and biotite of the metamorphic aureole are altered to sericite and/or chlorite. Igneous dikes and portions of the main stock are altered such that plagioclase is altered to sericite and kaolinite and biotite is altered to sericite, chlorite, and pyrite.

Associated rocks include Late Cretaceous granodiorite and porphyry of the Osgood Mountains pluton. Local rocks/geologic units include alluvial deposits.

Geology: Bagby and Cline (1991) offer preliminary results from research which indicate that confining pressures on the Getchell ore system varied from approximately 370-430 bars either during, or at some time subsequent to mineralization. These fluid pressures are greater than those which are normally accepted as epithermal.Geology comments: Bagby and Cline (1991) offer preliminary results from research which indicate that confining pressures on the Getchell ore system varied from approximately 370-430 bars either during, or at some time subsequent to mineralization. These fluid pressures are greater than those which are normally accepted as epithermal.

Regional geologic structures: Regional thrust faults to the north and NNW-trending faults.

Local geologic structures: Gold mineralization is generally found at the intersection of a number of high-angle and low-angle fault sets. The low-angle faults and associated folds are the result of Devonian and Permian-age compressional events and the higher angle faults and fracture sets formed during Tertiary extension. Mineralization is both structurally and stratigraphically controlled. The Getchell fault is a zone of overlapping fractures which have an overall strike of N10W. Hotz and Willden (1964) offer evidence for up to 3500 feet of left lateral strike slip displacement and only a relatively small amount of dip slip movement along the Getchell fault. McCollum and McCollum (1991) indicate that the sense of movement on the Getchell fault is right lateral. The Getchell Fault Zone is a complex system of sub-parallel, high angle faults which is at least 500 m wide. The zone is made up of a number of fault planes, separated by brecciated gouge and characterised by intense clay alteration, and by brecciation in the hanging wall.

The main Getchell deposit within the fault has been drilled to a depth of 600 meters down dip from the original surface, and remains open down dip. There is a 'Main Vein' which is a dominant structure with a distinct footwall, complexed by several conjugate veins to the west. Sub-parallel, mineralised structures have also been found up to 200 m into the footwall of this main structure, while alteration, fault gouge and mineralisation occur up to 500 meters to the east into its hanging wall (First Miss Gold Inc., 1993). Movement on the Getchell Fault has been both normal and dextral strike-slip (McCollum & McCollum 1990). On the basis of the relative displacement of the Palaeozoic sediments and the Cretaceous granodiorite of the Osgood Mountain Stock it is believed that the Getchell Fault is a reactivated older structure (D. Bond, Personal communication, 1993). The most recent displacement has taken place during the Miocene to present Basin and Range movement, representing further reactivation of an older structure. The fault cuts all three main stratigraphic units found within the pit, as well as the Osgood Mountain Stock. Altered blocks of granodiorite, rimmed by the skarn assemblage, are faulted downwards along the footwall structure into the Getchell Fault Zone and subsequently mineralised with gold (FirstMiss Gold Inc., 1993).

Workings included surface and underground openings. The mine has been developed by both underground and surface workings at various times during its production history. The Getchell deposit was developed by the North, Center, South, and Hansen Creek Pits. The Getchell underground is fully developed and is accessed from the Getchell open pit via two portals. The Getchell underground has a relatively short remaining mine life based on current proven reserves, although its life may be extended with the lower processing costs, additional exploration drilling, and engineering analysis. Mining methods for the Getchell underground is currently 100% drift-and-fill, as the last of the longhole ore was produced in 2005.

Production information: From 1938 to 1996 the Getchell property produced 66.8 kilotonnes of gold and more than 1.2 kilotonnes of silver from 18,361 kilotonnes of ore. In 1997, the remaining Getchell resource was estimated at 14,400 kilotonnes of ore containing 153 kilotonnes of gold and an unknown amount of Ag and As. This resource includes Getchell underground, stockpiles, unmineable resource in the Main pit, and North Getchell underground resource.

Analytical data results: Average ore grade 0.18-0.23 ounces per ton Au.

Reserve/resource data: August, 1997 - proven and probable reserves at the Getchell property, not including Turquoise Ridge, are 14.9 million tons grading 0.3 ounce Au/ton. Including Turquoise Ridge, the total mineral inventory is 10.9 million ounces Au.

Mineral List

Mineral list contains entries from the region specified including sub-localities
Acanthite
Aktashite
'Apophyllite'
Arsenic
Arsenolite
Arsenopyrite
Baryte
'Biotite'
Bismuthinite
Bornite
Calcite
Cassiterite
'Chabazite'
Chaidamuite
Chalcocite
Chalcopyrite
'Chlorite Group'
Christite
Cinnabar
Coloradoite
Copper
Covellite
Crandallite
Epidote
Epsomite
Ferrimolybdite
Fluorapatite
var: Carbonate-rich Fluorapatite
Fluorapophyllite-(K)
Fluorapophyllite-(Na)
Fluorite
Galena
Galkhaite
'Garnet'
Getchellite (TL)
'Gismondine'
Gold
var: Electrum
Graphite
Guérinite
Gypsum
Haidingerite
'Heulandite'
Hübnerite
'Ilsemannite'
Jarosite
Jordanite
Kaolinite
Kermesite
Laffittite
Lorándite
Magnetite
Malachite
Marcasite
Massicot
Melanterite
Meta-autunite
Metacinnabar
Metastibnite
Molybdenite
Muscovite
var: Sericite

Orpiment
Pararealgar
Pascoite
Pharmacolite
Picropharmacolite
Piemontite
Polhemusite
Pyrite
Pyrrhotite
Quartz
var: Amethyst
var: Chalcedony
Rauenthalite
Realgar
Rozenite
Scheelite
Scorodite
Silver
Sphalerite
'Stibiconite'
Stibnite
'Stilbite'
Symplesite
Tvalchrelidzeite
Wakabayashilite
Weilite
Wollastonite


116 entries listed. 73 valid minerals. 1 type locality (valid mineral).

Localities in this Region

USA

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References

Hardy, R. A. (1940), Geology of the Getchell Mine, AIME Technical Publication No. 1240, 3 pp.

Wise, F. and Wark, C. W. (1940), Metallurgy and milling practice at Getchell Mine, AIME Technical Publication 1260, 9 pp.

Erickson, R. L., Marranzino, A. P., Oda-Uteana, and Janes, W. W. (1964), Geochemical exploration near the Getchell Mine, Humboldt County, Nevada, USGS Bulletin 1198-A, 26 pp.

Weissberg, B. G. (1965): Getchellite, AsSbS3, a new mineral from Humboldt County, Nevada. American Mineralogist: 50: 1817-1826.

Jungles, G. (1974): Galkhaite: A newly described mineral from Siberia found at the Getchell mine, Nevada. Mineralogical Record: 5: 290-291.

First Mississippi Corp., Annual Reports for fiscal years (1983), 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991.

Nakai,I. & Appleman, D.E. (1983): Laffitite, AgHgAsS3, crystal structure & second occurrence from the Getchell Mine, Nevada, American Mineralogist: 68: 235-244

Berger, B. R. (1985), Geological and geochemical relationships at the Getchell Mine and vicinity, Humboldt County, Nevada, in Hollister, V. F., ed., Discoveries of epithermal precious metal deposits, case histories of mineral discoveries vol. 1, Society of Mining Engineers, New York: 51-59.

Berger, B. R. and Tingley, J. V. (1985), History of discovery, mining, exploration of the Getchell mine, Humboldt County, Nevada, in Hollister, V. F., ed., Discoveries of epithermal precious metal deposits, case histories of mineral discoveries vol. 1, Society of Mining Engineers, New York: 49-51.

Stolburg, C.S. and Dunning, G.E. (1985): The Getchell Mine, Humboldt Co. Mineralogical Record: 16(1): 15-23.

Dunning, Gail E. (1988), calcium arsenate minerals new to the Getchell Mine, Nevada, The Mineralogical Record: 19(4): 253-257.

Anthony, Bideaux, Bladh, Nichols (1990), "Handbook of Mineralogy", Vol. 1.

Bagby, W. C. and Cline, J. S.(1991), Constraints on the pressure of formation of the Getchell gold deposit, Humboldt County, Nevada, as interpreted from secondary-fluid-inclusion data, in Raines, G. L., et al, eds., Geology and Ore Deposits of the Great Basin, The Geological Society of Nevada, Reno: 793-804.

Madden-McGuire, D. J. (1991), Stratigraphy of the limestone-bearing part of the lower Cambrian to lower Ordovician Preble Formation near its type locality, Humboldt County, North Central Nevada, in Raines, G. L., et al, eds., Geology and Ore Deposits of the Great Basin, The Geological Society of Nevada, Reno: 875-893.

McCollum, L. B. and McCollum, M. (1991), Paleozoic rocks of the Osgood Mountains, Nevada, in Raines, G. L., et al, eds., Geology and Ore Deposits of the Great Basin, The Geological Society of Nevada, Reno: 735-738.

Economic Geology (1993): 88: 171-185.

Nevada Bureau of Mines and Geology (1994), MI-1993.

Nevada Division of Minerals (1994).

Economic Geology (1997): 92: 601-622.

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.

Bowell, R.J., Baumann, M., Gingrich, M., Tretbar, D., Perkins, W.F., and Fisher, P.C. (1999) The occurrence of gold at the Getchell mine, Nevada. Journal of Geochemical Exploration: 67: 127-143.

Cline, J.S. (2001) Timing of gold and arsenic sulfide mineral deposition at the Getchell Carlin-type gold deposit, northcentral Nevada. Economic Geology: 96: 75-89.

Placer Dome Gold Company website (2003).

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10045077, 10149626, 10173820, 10222671, 10222786 [mill], 10310488.

Getchell - Internet report by Porter eoconsultancy.

Nevada Bureau of Mines and Geology Special Publicaion 31, Minerals of Nevada.

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