Golden Sunlight Mine (Telluride and Excelsior; Moonlight Buffalo; Blue Moose; Minera Hill; Sunlight), Whitehall Mining District (Cardwell Mining District), Jefferson County, Montana, USAi

Regional Level Types
Golden Sunlight Mine (Telluride and Excelsior; Moonlight Buffalo; Blue Moose; Minera Hill; Sunlight)	Mine
Whitehall Mining District (Cardwell Mining District)	Mining District
Jefferson County	County
Montana	State
USA	Country

A former Au-Ag-Cu occurrence/mine located in the NE¼SE¼SE¼ sec. 19, T2N, R3W, MPM, on private land (fee ownership). Owned by Placer Dome Inc. (100%), Canada (1990-1995). Operated by Golden Sunlight Mines, Inc., Montana (1990-1995). MRDS database stated accuracy for this location is 100 meters. This property involves portion s of sections 19, 20, 28, 29 & 30, T2N, R3W, MPM.

The first claims were staked by A.H. Hedley in 1890. American Development and Mining Company acquired Hedley's claims and staked claims on Mineral Hill. A stamp mill was constructed in 1895 by American Developemnt. Milling efforts were not successful and were abandoned in 1905. During the period 1890-1910 ore was shipped to smelters from the "old Sunlight" workings. Estimated production for this period was 75,000 tons of ore having a gross value of $1,500,000 (period values). The property was sold in 1904 to Eugene Ring of Butte. A 40 ton cyanide mill was built in 1906 and was abandoned before 1910. During the period 1910 to 1917 the property was acquired by H.C. Bacorn and Associates and was mined on a small scale by lessees. In 1920 J.B. Wellcome and Alex McKay gained control of the property. Later, their heirs gave Anaconda Company an option to purchase the property. Anaconda declined after exploration in 1935. During 1936/1937 A.O. Smith obtained a lease and option to purchase the Sunlight holdings from Wellcome and McKay's heirs. Production of a small amount of direct shipping ore occurred in 1938. In 1939 Smith sub-leased the property and the lessees shipped small quantities of ore until 1946. The Martin Brothers tested the property in 1946 and gave up the option to purchase. During the period 1955 to 1956 White Development Company attempted to operate the mine as a moderate-volume, open pit operation A glory hole and a connecting conveyor belt haulage adit were developed on Mineral Hill to mine a low-grade ore body centered around the breccia pipe. American Exploration and Mining Company (Placer U.S.) optioned the property (predecessor of Golden Sunlight Mines) from A.O. Smith Corporation. Placer U.S. purchased the property in 1968. Construction of facilities started in 1981. During February, 1983, the first Au was poured after a $50 million capital investment. A 7½ month hiatus in production was realized due to a re-activated landslide.

Mineralization is a breccia pipe deposit hosted in the Early Pliocene Greyson shale of the Belt Series. The ore body is ellipsoidal in shape at a length of 500 meters, strike of N45W and a dip of 25E, at a thickness of 200 meters, width of 100 meters. ore body No. 1 is pipe-like and breccia filled. Ore body No. 2 is a fissure vein. The primary mode of origin was hydrothermal activity. Primary ore control was a latite porphyry intrusion. The Golden Sunlight Fault may also be an ore control. Wallrock alteration is intense. (not specified). Auriferous pyrite is associated with quartz veins. Mineralizing solutions apparently injected into irregular vein system. Associated rocks include Pliocene latite, lamprophyre dikes and latite porphyry stock. Local rocks include Tertiary sedimentary rocks, undifferentiated.

Regional geologic structures include the Boulder Batholith and the Lombard Overthrust. Local structures include the Golden Sunlight Fault that trends N-S and dips 45E.

Many faults cut both the igneous and sedimentary rocks. A pipe-like body of silica-cemented shale occurs at this deposit. The core of the mineralized zone is centered around the breccia pipe. Hydrothermal alteration within and surrounding the breccia pipe is evidenced by silicification and sericitization. Free gold is reported with minor silver. Pyrite is the dominant sulfide.

The Proterozoic sedimentary rocks contain synsedimentary mineralization in the form of high-sulfide horizons and finely disseminated diagenetic mineralization. Authigenic K-feldspar is also present. Samples of the synsedimentary mineralization that appear not to have been affected by the epigenetic processes carry low-level gold in the 0.01 ounce/ton (0.031 grams/ton) range. This suggests that the Au was deposited with the synsedimentary sulfides. This low-level Au may have served as the source for some of the metals in the epigenetic breccia pipe. The similar multi-element signature between the synsedimentary system and the breccia pipe also supports the possibility of epigenetic re-mobilization of the metals. (Foster and Smith, 1995 ?)

This property was developed by at least 15 adits and pits and several surface cuts on the E side of the ridge, including the "Bacorn" level or adit and the "Ohio" level or adit. Early mining was predominantly by underground workings. Open-pit started in 1981 to present (2000). This mine was slated for closure in 2002 (as of 6/2000).

Production information: 1989 production = 111,539 ounces Au from 2,268,000 metric tons of treated ore.

Milling was by size reduction, then cyanide vat leaching (twelve 400,000 gallon leach tanks, washing and treatment of slime fraction by carbon absorption using carbon-in-pulp tanks and up-flow carbon columns. The gold is removed from the carbon in pressure stripping vessels using a caustic cyanide solution. The sand fraction goes to a sand tailing retreatment using concentration in spiral shaped launders.

The tailings reprocessing project at Golden Sunlight continues to ramp-up and we expect the project to reach full production towards the end of 2024. The reprocessing of high-sulphide tailings eliminates the need for perpetual water treatment, providing a valuable fuel source for the Carlin roasters, and facilitating proper closure.

Other Databases

Link to USGS MRDS:	10148740

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References