Golden Sunlight Mine (Telluride and Excelsior; Moonlight Buffalo; Blue Moose; Minera Hill; Sunlight), Whitehall District (Cardwell District), Jefferson Co., Montana, USA
|Latitude & Longitude (WGS84):||45° 54' 20'' North , 112° 1' 16'' West|
|Latitude & Longitude (decimal):||45.90577,-112.02132|
|Owned/operated by:||Barrick Gold Corporation|
|Köppen climate type:||BSk : Cold semi-arid (steppe) climate|
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.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
55 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
- Igneous rock
- Sedimentary rock and sediment
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
1000 - 1600 Ma
|LaHood Formation: locally includes Table Mountain and Moose Formations in Highland Mountains|
Age: Mesoproterozoic (1000 - 1600 Ma)
Stratigraphic Name: LaHood Formation
Description: LaHood Formation: Dark gray, dark brown, reddish brown, coarse, arkosic conglomerate locally with very large clasts derived from crystalline metamorphic rocks. Grades from mega-clast conglomerate to shale or argillite over short distances. Thickness as much as 3,000 m (9,842 ft). In Highland Mountains - Table Mountain Formation: Very light gray quartzite and argillaceous quartzite. Thickness as much as 530 m (1,740 ft). Moose Formation: Silty argillite and siltite. Thickness as much as 90 m (295 ft).
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. 
1000 - 1600 Ma
|Quartzite of Queener Mountain, quartzite along Skalkaho Creek, Spokane Formation, and Greyson Formation, undivided|
Age: Mesoproterozoic (1000 - 1600 Ma)
Reference: Zientek, M.L., P.D. Derkey, R.J. Miller, J.D. Causet et al. Spatial Databases for the Geology of the Northern Rocky Mountains - Idaho, Montana, and Washington. U.S. Geological Survey Open-File Report 2005-1235 Version 1.0.