Lone Tree/Stonehouse Mine Area

Site Name

Primary: Lone Tree/Stonehouse Mine Area
Secondary: Wayne Zone (Lone Tree)
Secondary: NW-1
Secondary: East Zone
Secondary: Southeast Area (Stonehouse)

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Commodity

Primary: Gold
Secondary: Silver
Tertiary: Arsenic
Tertiary: Antimony
Tertiary: Mercury
Tertiary: Copper

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Location

State: Nevada
County: Humboldt
District: Battle Mountain District

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Land Status

Land ownership: BLM Administrative Area
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.
Administrative Organization: Winnemucca BLM District

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Newmont Gold Corp.
Info Year: 2005

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: sediment-hosted gold
Operation Type: Surface
Year First Production: 1991
Year Last Production: 2005
Discovery Year: 1989
Years of Production:
Organization:
Significant: Y
Deposit Size: M

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Physiography

Not available

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Mineral Deposit Model

Model Name: Distal disseminated Ag-Au

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Orebody

Form: tabular to irregular

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Dominant alteration types affecting the host rocks are silicification, argillization, and pyritization.

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Rocks

Name: Porphyry
Role: Associated
Description: altered quartz porphyry dikes
Age Type: Associated Rock
Age in Years: 39.000000+-
Age Young: Middle Eocene

Name: Porphyry
Role: Associated
Description: altered quartz porphyry dikes
Age Type: Associated Rock
Age in Years: 36.000000+-
Age Young: Late Eocene

Name: Porphyry
Role: Host
Description: quartz porphyry dikes
Age Type: Host Rock
Age Young: Tertiary

Name: Basalt
Role: Host
Description: metabasalt
Age Type: Host Rock
Age Young: Early Permian
Age Old: Middle Pennsylvanian

Name: Chert
Role: Host
Age Type: Host Rock
Age Young: Early Permian
Age Old: Middle Pennsylvanian

Name: Siltstone
Role: Host
Age Type: Host Rock
Age Young: Early Permian
Age Old: Middle Pennsylvanian

Name: Sandstone
Role: Host
Age Type: Host Rock
Age Young: Early Permian
Age Old: Middle Pennsylvanian

Name: Conglomerate
Role: Host
Age Type: Host Rock
Age Young: Early Permian
Age Old: Middle Pennsylvanian

Name: Quartzite
Role: Host
Age Type: Host Rock
Age Young: Ordovician

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Arsenopyrite
Ore: Pyrite
Gangue: Chalcopyrite
Gangue: Marcasite

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Comments

Comment (Development): Drilling at Lone Tree was conducted near the completion of a much larger drilling program in the South Valmy Area. Holes at Lone Tree were sited in part on drilling results at the Stonehouse Deposit immediately to the south and in part on geologic factors considered since 1987. The discovery hole, TH-79, was drilled in July, 1989. It intersected 35 feet of ore grading 0.12 ounces of gold per ton starting at a depth of 140 ft. A follow-up reverse circulation drilling program of 10 holes was begun in August, 1989. These were angle holes drilled mainly as east-west fences in the vicinity of TH-79. Of these 10 holes, only 1 failed to intersect significant au mineralization. By December, 1989, the known strike length of the au-bearing structure extended nearly 0.5 mile on Santa Fe Pacific property. An accelerated drilling program beginning in January, 1990, used as many as 17 drill rigs simultaneously. The goal was to delineate an oxide resource by June, 1990. The presence of power lines on the property was a hindrance to the siting of the drill holes. Prior to mine development, these power lines were moved at a cost of $4 million. The production decision was made May, 1990, construction began in December, 1990, full scale mining began April, 1991, and the first dore was poured august, 1991. Over 400 drill holes had been completed at Lone Tree as of April, 1992. The project capital cost was $52.9 million, excluding initial exploration. Cash costs in 1991 were $103.45/oz. Au. A mill equipped with a low temperature, low pressure autoclave to treat sulfide ore was built in 1994 at an estimated cost of $67 million. Newmont acquired Santa Fe Pacific Gold Corporation in 1997, adding Lone Tree and other deposits near Winnemucca to its portfolio.

Comment (Deposit): At Lone Tree, the Power Line Fault is the principal ore host and is equivalent to the NW-1 structure identified at the Stonehouse Deposit to the south. Gold mineralization at Lone Tree occurs in all three rock units (Valmy Formation, Antler Sequence, and Havallah Sequence) and is largely confined to a N-S trending zone of intense fracturing and faulting known as the Wayne Zone. The Wayne Zone dips steeply to the west and has been traced for nearly a mile along strike on the lone tree property. Major cross structures offset and pinch the Wayne Zone at the northern and southern ends of Lone Tree Hill.In sulfide ore, gold is associated mainly with arsenopyrite and to a lesser extent with one or two generations of pyrite. Overburden ranges from 1 foot to 200 feet thick. At Stonehouse, the NW-1 structure is the most economically important structure. Gold mineralization occurs in three main areas: the main NW-1 structure has been defined over almost 1.5 miles, strikes NNW, and dips 70-75 west. East Zone mineralization lies east of NW-1, in its footwall. The east zone is a series of horsetail structures that strike approx. N-S and have steep west to almost vertical dips. The Southeast zone is offset approximately 1000 feet from the NW-1 structure. Gold values have been encountered over a broad area in the Southeast zone with some suggestion of a relatively flat-lying ore body. Mineralization in the Southeast zone tends to be erratic, low grade, and refractory.

Comment (Economic Factors): Production from Lone Tree and Stonehouse from 1991-2002 was 2,149,832 ounces of gold, and 208,326 ounces of silver in 1995 and 1998-02. In 2002 the deposits contained proven and probable reserves of 21 million tons of ore grading 0.069 ounces of gold per ton. There was also measured and indicated mineralized material of 2 million tons grading 0.057 ounces of gold per ton. There was an additional million tons of inferred mineralized material grading 0.047 ounces of gold per ton.

Comment (Identification): This record incorporates all material from earlier records for the same deposit: MRDS # RE00041 and RE00042 as well as additional material.

Comment (Location): The Lone Tree and Stonehouse deposits are located at Lone Tree Hill within a mile of Interstate 80.

Comment (Commodity): Gangue Materials: chalcopyrite, marcasite

Comment (Workings): The project area incorporates all or part of four sections which were 100% owned by Lone Tree Mining, Inc., a subsidiary of Santa Fe Pacific Minerals, until it was taken over by Newmont mining in 1997. Ore is segregated into oxide heap leach, sulfide mill, and run-of-mine heap leach. Conventional heap leaching methods are utilized to recover up to 90% of the gold in the oxide heap leach ore. Run-of-mine heap leach recovery is only expected to be 40%, but the low cost of this process allows treatment of the lower grade ore at a profit. Sulfide ore is being stockpiled. Expected mine life in 1992 was 12 years.

Comment (Commodity): Ore Materials: Gold, arsenopyrite, pyrite.

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References

Reference (Deposit): Braginton, B., 1992, Lone Tree Mine, abstract in April, 1992 Geological Society of Nevada Newsletter.

Reference (Deposit): NBMG Map 91, 3rd edition.

Reference (Deposit): Braginton, B., 1992, Lone Tree Mine, oral presentation at April 17, 1992 meeting of the Geological Society of Nevada.

Reference (Deposit): Mining Journal/Montagu Mining Finance, Mining Database, 8/10/91.

Reference (Deposit): American Mines 1996-2001

Reference (Deposit): NBMG, MI-1989-MI-2003

Reference (Deposit): Nevada Division of Minerals, 1994

Reference (Deposit): The Mining Record, Aug 4,1993

Reference (Deposit): McGibbon, D.H., 1992, The Stonehouse Gold Deposit, Humboldt County, Nevada, abstract in April, 1992 Geological Society of Nevada Newsletter.

Reference (Deposit): McGibbon, D.H., 1992, The Stonehouse Gold Deposit, Humboldt County, Nevada, Oral Presentation at April 17, 1992 meeting of the Geological Society of Nevada.

Reference (Deposit): NBMG, 1994, MI-1993

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.

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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.