The Natural Bridge mining district is located in Park County on the East Boulder Plateau on the northeast slopes of the Beartooth Mountains. The area that was most heavily prospected in the district is known as Placer Basin, in the East Fork of the Boulder River drainage. Ores in the area contained gold, silver, and copper but there is little information available on production (Sahinen 1935).
The district is a 48-square-mile area that lies mostly east of the Boulder River. The West Fork of the Stillwater River runs through the southeast corner of the district. The area is one of high relief. The district is on the northeastern flank of the Beartooth uplift. The southern part of the region is "occupied by a complex of Archean rocks which, to the northeast, are overlain by steeply tilted Paleozoic sediments." The Placer Basin area has sulfide-rich rocks associated with the Basal series of the Stillwater Complex (Page et al. 1985; Sahinen 1935).
As of 1935, the production from the district referred to by Sahinen (1935) as Natural Bridge consisted only of test shipments.
In 1957 U. S. Steel built a road from the Upper Boulder to Iron Mountain and began strip mining. Since then, rather extensive mining operations have occurred in Placer Basin on the plateau above Graham Creek (Staunton and Keur 1975).
BOUNDARIES OF THE DISTRICT
The Natural Bridge mining district appears to have been fairly large during the historic period, generally extending farther north than the district as defined today by the AMRB (1994). It was created out of the Independence district that was flourishing to the south. By 1895 the miners had established a new district called Natural Bridge "to cover the territory north of Boulder District down to the contact at Cowan's" (shown as Contact on modern maps) (Freeman 1895).
According to the U. S. Bureau of Mines (1989):
Early in its history, the Independence mining district extended as far as 20 mi to the north; however, the Natural Bridge area later became a separate district.
The "Natural Bridge" claim, located near the mining town of Contact, is actually within the Boulder River mining district. The Natural Bridge, a rock formation on the Boulder River, is also located near Contact.
According to a USGS report (1983), the Natural Bridge district includes much of the area to the west of the Boulder River, from Froze-to-Death Creek to Great Falls Creek, and the Gish Mine east of the river. Sahinen (1935) describes the district more generally as being located on the Boulder River 25 miles southwest of Big Timber.
HISTORIES OF SELECTED MINES
No historic mines have been identified within 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
Anthro Research, Inc.
1990 "Additional Cultural Resource Evaluations in the East Boulder and Placer Basin Areas of Sweet Grass County, Montana."
Bureau of Mines
1989 "Mineral Resources of the Central Part of the Independence Mining District, Park and Sweet Grass Counties, Montana." Mineral Land Assessment, 4-89.
Freeman, Henry C.
1895 "Boulder Mining District, Montana",
Eng. and Min. Journal
, Vol. 60, pp. 583-584.
1912 Mineral Resources, p. 765.
1917 Mineral Resources, p. 359.
Page, Norman J. et al.
1985 "Exploration and Mining History of the Stillwater Complex and Adjacent Rocks," in Gerald K. Czamanske and Michael L. Zientek, eds.,
The Stillwater Complex, Montana: Geology and Guide.
Montana Bureau of Mines and Geology, Special Publication 92.
Sahinen, Uuno Mathias
Mining Districts of Montana
. M. S. thesis, Montana School of Mines. Staunton, Ruth, and Dorothy Keur
1975 Jerkline to Jeep: A Brief History of the Upper Boulder. Harlowton, MT: Times Clarion.
U. S. Geological Survey and U. S. Bureau of Mines
1983 Mineral Resources of the North Absaroka Wilderness Study Area, Park and Sweet Grass Counties, Montana. Washington, DC: Government Printing Office, Geological Survey Bulletin 1505.
Western Mining World
ca. 1903 Vol. 17, no. 8, p. 14.