The Sapphire mining district is located east of Hamilton and Darby in the Bitterroot Valley and in the adjacent Sapphire Mountain range. Mining in the area has been insignificant.
According to a geological map of Ravalli County, sedimentary rocks of the Newland formation of the Belt series underlie the northeastern part of the Sapphire district. These are bordered on the west and south by intrusives from the Idaho batholith, which underlies most of the district. Alluvium covers the Bitterroot River valley and the lower stretches of its tributaries, with the largest area being the flat expanse of land east of Hamilton (Sahinen 1957).
There is no reported placering in the Sapphire district. The only mineral that has been explored is a vermiculite deposit on Gird Creek, about 11 miles east of Hamilton. S. H. (Swift) Chamberlain and G. H. Garnett made the discovery in 1930, and during the next three years they tested the deposits with several shallow pits and short adits. The mine received minimal development and the company set up a small exfoliation plant in Hamilton to process and market the expanded product. The mine and mill had closed by 1953, and it is unknown if they reopened (Sahinen 1957; Perry 1948; Trauerman and Reyner 1950).
BOUNDARIES OF THE DISTRICT
The boundaries of the newly formed district are not described in current mining literature. As defined by the AMRB (1994) it encompasses the drainages of Willow, Gird, Skalkaho, Sleeping Child, and Rye creeks (Figure 1). It is bordered by Burnt Fork district on the north, Bitterroot on the west, Sula on the south, and Frog Pond Basin and Rock Creek on the east.
HISTORIES OF SELECTED MINES
Gird Creek Vermiculite Products Co.
The Grid Creek vermiculite mine is located about 11 miles east of Hamilton in section 19, T6N, R18W. The deposit, however, covers more area, extending into sections 20, 29, and 30 in T6N, R18W, and sections 24 and 25, T6N, R19W (Sahinen 1957).
S. H. (Swift) Chamberlain and G. H. Garnett discovered the vermiculite deposits in 1930. They tested them in several areas by digging shallow pits and short adits, one of which extended 50 feet. The mine was developed only minimally with open pits, and a small quantity of ore was processed at a plant in Hamilton. The company reported operations in 1949. At the time of his visit in 1953, however, Sahinen noted that neither the mine nor the mill were active, and it is unknown if they ever resumed operations (Sahinen 1957; Perry 1948; Trauerman and Reyner 1950).
According to Perry (1948), the "vermiculite occurs in an intrusion of pyroxenite...which cuts impure limestone and argillite of the Newland formation of the Belt series of pre- Cambrian age. Associated with the pyroxenite are intrusive masses of syenite and also pegmatite dikes." The deposits are similar to those found near Libby. Tests on samples of ore showed that one that weighed 86.6 pounds per cubic foot before treatment weighed just 11.2 pounds per cubic foot after expansion (Perry 1948).
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
Perry, Eugene S.
1948 "Talc, Graphite, Vermiculite and Asbestos Deposits in Montana",
Memoir No. 27
. Montana Bureau of Mines and Geology, Butte.
Sahinen, Uuno Mathias
1957 "Mines and Mineral Deposits, Missoula and Ravalli Counties, Montana",
Bulletin No. 8
. Montana Bureau of Mines and Geology. Montana School of Mines, Butte.
Trauerman, Carl J., and Millard L. Reyner
1950 "Directory of Montana Mining Properties, 1949",
Memoir No. 31
. Montana School of Mines, Butte.