The district is unimportant in production and none has been reported since 1904, although some placer operations may have been conducted on Slough Creek during the mid-1930's. The district is just north of Yellowstone Park in rugged Absaroka Mountain range, an area of high relief. The primary focus of mining was Slough Creek where placer gold was recovered from the gravels Samples taken from prospect dumps on Horseshoe Mountain detected pyrite as the only metallic mineral (Sahinen 1935; Lyden 1948).
The prevailing rocks of the region are pre-Cambrian gneisses and schists are cut by andesite and dacite intrusives. Horseshoe Mountain is composed of a dacite or andesite porphyry intrusive into the gneisses. Some Cambrian sedimentary rocks are exposed unconformably overlying the gneiss a few miles west of Haystack Mountain. To the west and south Cambrian and pre-Cambrian rocks are covered by andesite breccias and flows. Ore deposits occur in veins cutting both the porphyrite intrusive and the gneiss. The ores carry gold and silver. Some copper ores have been found at the head of Slough Creek. The area has also been impacted by Pleistocene mountain glaciation, scraping away significant gravel deposits and limiting placer and dredging operations (Sahinen 1935; Lyden 1948).
BOUNDARIES OF THE DISTRICT
Sahinen (1935) places the district at the headwaters of Slough Creek, in the vicinity of Horseshoe Mountain. It is 60 miles east of Gardiner, the terminus of the Yellowstone Park branch of the Northern Pacific Railroad, and 10 miles west of Cooke City.
Lyden (1948) notes that the placers in Slough Creek originate from gold, silver and copper veins found in the intrusives and gneisses of the Horseshoe district.
Figure 1 shows the Horseshoe district as defined by the AMRB (1994) with the smaller area around Slough Creek as defined by Sahinen (1935) and Lyden (1948).
HISTORIES OF SELECTED MINES
No mines have been reported in this district.
Abandoned Mine Reclamation Bureau (AMRB)
1994 Mining districts of Montana. Maps 1:100,000 and Map #94-NRIS-129. Compiled and edited by Joel Chavez. Prepared by Montana State Library
Natural Resource Information System (NRIS) for Montana Department of State Lands. Helena GCM Services, Inc.
1985 "Cultural Resource Inventory and Evaluation of the McLaren Mill Site, Cooke City, Montana (Supplement to the September 1985 Report on Abandoned Hardrock Mines Sites in Western Montana)", prepared for the Montana Department of State Lands. Ms. on file, Butte.
GCM Services, Inc.
1990 "Cultural Resource Inventory and Assessment the New World Mining Project Park County, Montana", prepared for Hydrometrics, Inc. Ms. on file, Butte.
Lyden, Charles J.
Gold Placers of Montana,
Montana Bureau of Mines and Geology, Butte, Reprint 6, 1987.
Reed, Glenn C.
1951 "Mines and Mineral Deposits (except fuels), Park County, Montana",. U. S. Department of the Interior.
Bureau of Mines Information Circular 7546
Rubel, Daniel Nicholas
1964 "Geology of the Independence Area, Sweet Grass and Park Counties, Montana." Ph. D. dissertation, University of Michigan.
Sahinen, Uuno Mathias
Mining Districts of Montana
, A Thesis Submitted to the Department of Geology in Partial Fulfillment of the Requirements for the Degree of Master of Science in Geological Engineering.
Swallow, G. C., J. B. Trevarthen and Jacob Oliver
Reports of Inspectors of Mines, State of Montana, year ending November 30th, 1890
. Journal Publishing Company, Helena.
U. S. Geological Survey and U. S. Bureau of Mines
Mineral Resources of the North Absaroka Wilderness Study Area, Park and Sweet Grass Counties, Montana
. Washington, DC: Government Printing Office, Geological Survey Bulletin 1505.
Wolle, Muriel S.
Montana Pay Dirt. A Guide to the Mining Camps of the Treasure State
. Sage Books, Denver.