Tonopah Divide Gold and Silver Project

Site Name

Primary: Tonopah Divide Gold and Silver Project
Secondary: Divide Mine
Secondary: Tonopah Divide Mine
Secondary: Gold Mountain
Secondary: Gold Hill Mine
Secondary: Falcon Exploration Mine and Mill

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Commodity

Primary: Silver
Primary: Gold
Tertiary: Molybdenum
Tertiary: Lead
Tertiary: Zinc
Tertiary: Copper

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Location

State: Nevada
County: Esmeralda
District: (Gold Mountain District)

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Land Status

Land ownership: Private
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Tonogold Resources Inc.
Info Year: 2006

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: vein/lode
Operation Type: Surface-Underground
Year First Production: 1918
Year Last Production: 1980
Discovery Year: 1901
Years of Production:
Organization:
Significant: Y
Deposit Size: S

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Physiography

Not available

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Mineral Deposit Model

Model Name: Epithermal vein, Comstock

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Orebody

Form: TABULAR

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Structure

Type: L
Description: A conspicuous set of northwest trending, high angle, right-lateral strike-slip faults bisect the Tonopah Divide district. The Tonopah Divide shaft developed the Divide lode which occupies the large Divide fault (Boden, 1992). On the west side of Gold Mountain the Mormon Girl fault appears to be a parallel right lateral fault of this set. Between these major faults are transcurrent north-northeast trending faults which accommodated minor right-lateral strike-slip motion. These fault sets clearly postdate earlier gold mineralized faults of the E-W trending and north dipping Gold Zone. The Gold Zone is parallel to and an easterly extension of the N 80?E listric Kernick fault on Hasbrouck Mountain. Gold-silver mineralization is known to occur almost exclusively in the hangingwall of the Gold Zone-Kernick fault system in the Divide district. Many of the mineralized faults found in the hangingwall of the Gold Zone are WNW trending high angle faults which may have fed the basal Siebert tuff unit. Interestingly Erdman (1992) noted a 'NW striking (more westerly?) gold bearing silicified fault was mapped that offset the Divide lode at the south end of the Falcon Pit'. This further suggests that at least some Gold Mountain mineralization occurred after the Divide fault ceased its right lateral motion.

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Alterations

Alteration Type: L
Alteration Text: Host rocks have been affected by minor silicification, sericitization, oxidation, pyritization with potassic, phyllic, and propylitic alteration zones around faults and fractures.

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Rocks

Name: Andesite
Role: Associated
Age Type: Associated Rock
Age Young: Pliocene

Name: Volcanic Breccia (Agglomerate)
Role: Associated
Age Type: Associated Rock
Age Young: Tertiary

Name: Rhyolite
Role: Associated
Age Type: Associated Rock
Age Young: Miocene

Name: Rhyolite
Role: Associated
Description: intrusive
Age Type: Associated Rock
Age Young: Miocene

Name: Felsic Volcanic Rock
Role: Associated
Description: rhyolitic
Age Type: Associated Rock
Age Young: Miocene

Name: Felsic Volcanic Rock
Role: Host
Description: rhyolitic
Age Type: Host Rock
Age Young: Miocene

Name: Felsic Volcanic Rock
Role: Host
Description: rhyolitic
Age Type: Host Rock
Age Young: Miocene

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Analytical Data

Not available

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Materials

Ore: Adularia
Ore: Sericite
Ore: Tetrahedrite
Ore: Galena
Ore: Chalcopyrite
Ore: Sphalerite
Ore: Ferrimolybdite
Ore: Powellite
Ore: Molybdenite
Ore: Argentite
Ore: Cerargyrite
Ore: Gold
Ore: Kaolinite
Ore: Quartz
Ore: Pyrite
Gangue: Limonite

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Comments

Comment (Development): The Tonopah Divide was originally mined on a small scale for gold since 1902; the Tonopah-Gold Mountain Mining Company was organized in 1902 to mine gold on the property. George Wingfield and Brougher reorganized it in 1912 as the Tonopah-Divide Mining Co. A rich silver lode was unexpectedly encountered in 1917. A Mr. T. Williamson was owner and operator in 1931. This has been the district's biggest producer. There was much exploration activity in the district in the 1970s and 1980s. The property was listed as an active, open pit, gold-silver mine in 1981, employing a total of 40 persons. The property was owned by Ebco Enterprises in 1983, and by Crown Resource Corp in 1987. Falcon Exploration acquired the Tonopah Divide property in 1978. The first load of ore was hauled July 17, 1981 and Falcon Exploration was mining 1000 tons per day from the property in 1981. It was a cyanide heap leach operation expected to last 5 years in 1981. Falcon proceeded to mine over 100,000 tons from the Falcon pit on the Divide lode between 1983 & 1985. In 1990 Echo Bay's Gold Zone drill program encountered discontinuous low grade mineralization across much of the length of Gold Mountain. In 1992 Corona Gold briefly controlled Hasbrouck Mountain, Tonopah Divide and Hill of Gold, but their drill program was cut short by Corona's merger with Homestake Mining following the 1992 acquisition of the Eskay Creek property. Hasbrouck was assigned briefly to Prime Resources, and then reverted in 1993 to underlier Euro-Nevada Corp, which discovered the high grade Ken Snyder Mine at Midas soon thereafter. In 1996 Euro-Nv returned to drill 18 holes on outlying targets some of which had previously been recommended by Dr. Ken Snyder. The best, although low grade, results were reported from Eliza Jane patent adjoining the Tonopah Divide's Little Zoe claims on the north. The Tonopah Divide Mining Co. controlled the property in 2001, and in 2006 Tonogold Resources signed a 10 year mining lease with the Tonopah Divide Mining Company. This lease covers 33 patented claims and 55 unpatented claims comprising the heart of the Tonopah Divide Mining District. Tonogold has subsequently staked an additional 69 claims and most recently purchased the Amazon claim. The total land package currently comprises 3,160 acres (2006)

Comment (Economic Factors): In 1988, the property contained a reported 500,000 tons of material with a grade of 0.04 ounces of gold per ton and 0.4 ounces of silver per ton. In 1997 it was reported at 1.8 million tons of material grading 0.55 ounces of gold per ton.

Comment (Deposit): Critical ages relations between mineralization and various units: The known mineralizing event at Tonopah Divide post-dates the intrusion of the Oddie Rhyolite K-Ar dated at 16.4-16.9 Ma. (Silberman, et. al., 1975). The post-mineral Brougher rhyolite at 16.1-16.3 Ma crosscuts veins on the north-side of the Tonopah Divide district. Adularia from Hasbrouck Mountain returned K-Ar dates at 16.1-16.4 Ma (Graney, 1985) and is believed to accurately represent the timing of the Tonopah Divide mineralizing event. The Tonopah Divide mineralizing event is considered contemporaneous with the second mineralizing (Three Hills) event in the Tonopah District. The Siebert Formation, dated at 16.9-17.1 Ma, is mineralized at the Tonopah Divide district and is best known as the host for mineralization at Hasbrouck Mountain (Silberman, et. al., 1975). The basal Siebert 'bouldery conglomerate' appears to have absorbed silica flooding during the 16.1-16.4 Ma mineralizing event. Since Tonopah district mine working closed before dating methods were perfected, very few dates of main stage Tonopah veins have been attempted. However, the best available data suggest this early stage occurred between 18.1-19.1 Ma. The upper Tonopah King member of the Fraction tuff, which unconformably underlies the Siebert Fm. in the Tonopah district, was dated at 18.7 Ma and is thought to be entirely pre-mineral relative to the early stage Tonopah productive veins. The earliest Fraction tuff was deposited as early as 20.5 Ma and is clearly pre-main Tonopah vein stage. Early stage veins were exclusively mined from the underlying Mizpah andesite dated at 22(?)- 20.5 Ma. One important ramification of these dates is that mineralized structures hosting the main stage Tonopah veins would not necessarily be expressed in units younger than the Tonopah King member of the Fraction tuff. If an older stage of mineralization underlies Tonopah Divide district, one would be well advised to scrutinize the Tonopah King and Tonopah Summit members of the Fraction tuff for a evidence of this event.

Comment (Location): In 2006, the property consists of 34 patented claims and 124 unpatented claims accessible by a maintained dirt road directly off US Highway 95.

Comment (Workings): VERTICAL SHAFT 600 FT DEEP WITH CROSSCUTS TO LODE ON 165, 265, 365, 470, 580 FT LEVELS (1921) DRIFTS RUN ALONG THE LODE FROM THE CROSSCU TS. VERTICAL SHAFT HAD ATTAINED DEPTH OF 1445 FT. BY 1923 OPEN PIT (1981). OPEN PIT IS JUST SE OF THE OLDTONOPAH DIVIDE SHAFT.

Comment (Geology): The Tonopah Divide district lies in Miocene and younger volcanic rocks of the San Antonio Range. Tonopah Divide shares nearly all the same volcanic rock types, similar styles of alteration and similar styles of silver and gold mineralization with the adjoining, prolific Tonopah district. The Tonopah Divide district lies in the southern portion of a major Miocene volcanic center which has been extensively studied within the Tonopah district. In this Miocene volcanic center a series of mostly rhyolitic intrusions, cross-cutting breccias, domes and other bodies have been spatially linked to both earlier silver-dominated and later gold-dominated mineralizing events. Some of these rhyolitic bodies were emplaced along shallowly westward-dipping, northwest trending normal faults while others intruded a series of mostly east-west trending high angle normal faults. Following mineralization, the Tertiary volcanic rocks were tilted gently to the west.

Comment (Identification): This record contain all data from record # M242087.

Comment (Deposit): Gold Mountain Au-Ag mineralization and Exploration Potential: Previous drilling has been skewed heavily toward the east flank of Gold Mountain in the vicinity of the Falcon pit. The Tonopah Divide mine was centered on the NW trending Divide fault at its point of intersection with the north-dipping Gold Zone fault system. Knopf (1921) felt that much of the Divide lode ore body was attributable to supergene enrichment. Sooty acanthite was noted coating pyrite along this fault to a depth between the 300 and 400 foot levels on the Divide Fault (Knopf, 1921). Below this level very little Ag-Au mineralization was mined, although the Tonopah Divide shaft was extended to a depth of over 400m. A second cluster of holes on Gold Mountain was drilled on a westerly spur known as Sealy Ridge. Fewer holes penetrated the intervening segment of the Gold Zone lying between the Divide pit and Sealy Ridge and on the northern flank of Gold Mountain. Cross sectional resource calculations by Johnson (2002) and Cartwright (1998) indicate that the density of drilling is not sufficient to adequately define the Gold Mountain resource. In the East Gold Zone greater drill hole density suggests the continuity of gold mineralization within the Oddie Rhyolite and associate breccias is questionable. Gold is associated with both silicification and potassic alteration in veins and breccia bodies along the Gold Zone fault system. Overall, the gold grade appears to be low (<.02 opt Au) and many of the intercepts are narrow. The Gold Zone dips moderately to steeply to the north and appears to widen where crosscut by northerly trending structures. There is minor evidence that the Gold Zone fault may flatten on its west end with depth in a fashion similar to the Kernick fault (Boden, 1992). The basal Siebert tuff has not been adequately drill tested above the Gold Zone fault at Gold Mountain. Hole GM_10_90 cut 18.3m @ 0.015 opt Au interpreted to lie near the top of the basal Siebert tuff at a vertical depth of about 130m. As the Siebert dips gently to the south on the north flank of Gold Mountain, potential exists to outline a sizeable oxide tonnage of gold mineralized basal Siebert in this area. The old Highway 95 Gap area: Drilling by Echo Bay (1990), Corona Gold (1992) and Euro Nv (1996) cut significant thicknesses of low grade gold mineralization above the Siebert-Fraction contact along a WNW trending normal faults on the Eliza Jane patent. In 1997, Phelps Dodge drilled three shallow rotary holes on the Amazon Patent which returned gold mineralization at and below the Siebert-Fraction tuff contact. Up to 49m of low grade gold mineralization was encountered and oxidation was found to extend from 76m to 107m below surface. TONOPAH-DIVIDE LODE HAS WELL-DEFINED WALLS. 13 CLAIMS COVERING 150 ACRES IN 1921 GOLD MOUNTAIN GOLD VEIN IS ON TONOPAH-DIVIDE PROPERTY. GOLD VEIN IS 0.5 FT WIDE, CARRYING $40/TON AU (1921)

Comment (Commodity): Ore Materials: native gold, cerargyrite, argentite; molybdenite, powellite, ferri-molybdite, sphalerite, chalcopyrite, argentiferous galena, tetrahedrite(?), copper oxide minerals

Comment (Commodity): Gangue Materials: limonite, sericite, pyrite, adularia, quartz, kaolinite

Comment (Deposit): The geology of the Divide District has been described in some detail by Knopf (1921), Alpers and Stewart (1972), Bonham and Garside (1979) and Erdman (1992). Erdman (1992) mapped and compiled the geology of the Divide district near Gold Mountain at the center of the Tonopah Divide property). Erdman (1992) describes the volcanic succession locally as being underlain by the Fraction tuff. Bonham and Garside (1972) described the lower Fraction tuff locally as the Tonopah Summit member consisting of poorly welded to unwelded vitric-lithic quartz latite to rhyolite. The Tonopah Summit member exceeds one thousand feet in thickness in the Tonopah district; its base is not exposed in the Divide district. Bonham and Garside (1972) stated that the upper Fraction tuff, the King Tonopah member is missing in the Divide district; however, Boden (1992) indicated it was present. Phelps Dodge drilled a 610m core hole east of the Falcon pit entirely within the Fraction tuff (Boden, 1992). The Fraction tuff is overlain by the Siebert Formation which consists of a variety of interbedded volcaniclastic sedimentary and air fall tuffaceous debris. The Siebert has been estimated at 180 meters thick on Siebert Mountain near Tonopah; however, Erdman (1992) describes a 300m section at Gold Mountain. The basal portion of the Siebert consists of tuffaceous sandstone to bouldery conglomerate derived largely of underlying Fraction tuff (Bonham et al, 1979). This basal unit is frequently silicified where exposed in the Divide district. The middle unit consists of 275 meters of ash flow and air fall tuff intercalated with epiclastic, volcaniclastics and lacustine sediments (Erdman, 1992). The upper unit was described by Erdman (1992) as a heterolithic tuff. The Oddie Rhyolite was intruded into the Siebert tuff on Gold Mountain, High Divide and other locations in the Divide district. It consists of flow banded rhyolite containing 10 to 15% quartz, sanidine, sodic plagioclase and minor biotite phenocrysts. The Divide andesite was also intruded farther to the southeast, roughly contemporaneously with the Oddie Rhyolite. The Brougher rhyolite is exposed in the northern Divide district and is believe to post date the previous two units.

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References

Reference (Deposit): Tonopah Times Bonanza, Oct 25, 1974.

Reference (Deposit): The Northern Miner, 1980.

Reference (Deposit): Tonopah Times Bonanza, Aug. 6, 1981

Reference (Deposit): The Mining Record Newspaper, Aug. 26, 1981, "Falcon Exploration Reopens Nevada Gold Hill Mine."

Reference (Deposit): Smith, A.M., and Carpenter, Jay, 1931, Unpublished notes on inspection trip to Tonopah Divide Mine; NBMG File 87, item 1.

Reference (Deposit): http://www.tonogold.com/s/TonopahDivide.asp
URL: http://www.tonogold.com/s/TonopahDivide.asp

Reference (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.

Reference (Deposit): Weed, W.H., Ed., 1920, The Mines Handbook, Vol XIV, p. 1162-1164

Reference (Deposit): NBMG Report 33, p. 124.

Reference (Deposit): State Inspector of Mines, 1981, Directory of Nevada Mine Operations Active in Calendar Year 1981

Reference (Deposit): NBMG Bull 92, p. 121-128

Reference (Deposit): Albers, J.P. and Stewart, J.H., 1972, Geology and Ore Deposits of Esmeralda County, NV; NBMG Bull. 78.

Reference (Deposit): Knopf, Adolph, 1921, The Divide Silver District, Nevada; USGS Bull. 715, p. 147-170.

Reference (Deposit): Garside, L.J. and Tingley, J.V., 1982, Field Examination, NBMG, 26 Mar 82

Reference (Deposit): Eureka Sentinel, 1972.

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Nevada Gold

Nevada has a total of 368 distinct gold districts. Of the of those, just 36 are major producers with production and/or reserves of over 1,000,000 ounces, 49 have production and/or reserves of over 100,000 ounces, with the rest having less than 100,000 ounces. Read more: Gold Districts of Nevada.