The Garrison district has produced little if any metallic ore. However, the district has been a prolific producer of phosphate. Deposits containing 60 percent tricalcium phosphate are located six to ten miles from the town of Garrison. Outcrops can be traced from Avon west to Drummond. It has been estimated that 100 million long tons of material have been removed from the district for the manufacture of fertilizer (Montana Bureau of Mines).

The Phosphoria formation is 65 to 70 feet thick in this district and the Retort phosphate member is three to five feet thick. In the eastern part of the district the Retort member is high-grade oolitic phosphorite as much as five feet thick. West of Garrison the phosphate sediments give way to fine sandstone, indicating the presence of an ancient shoreline.

The Garrison Mining & Phosphate Co. has developed a portion of the district emplacing 1,700 feet of crosscuts and drifts to produce phosphate rock for its plant in Trail, British Columbia.


Traditional sources of information on historic precious metal mines do not discuss the district. Sahinen (1935) does not place the district, nor is any mention made in Lyden (1948) or Wolle (1963).

Popoff and Service (1965) place the district north of Drummond, Garrison and Avon in Granite and Powell counties.

Figure 1 shows the district as defined by the AMRB (1994) which is in accordance with Popoff and Service (1965).


Anderson - Brock

The Anderson mine is located in sections 2 and 3 in T10N, R10W on the east fork of Brock Creek. Throughout its history the mine has been owned by the Montana Phosphate Products Co. It is the largest underground producer of phosphate rock in the "Western field" and the deepest such operation in the United States. Development on the Anderson sector of the mine began in 1929; the Brock sector began development in 1955. At one point the operations employed 180 men in two shifts and produced 1,200 tons of rock per day. Total production of the Anderson mine since 1929 was estimated to be over 4,500,000 long tons with the majority of production after 1945. The mine was developed for more than 9,000 feet on the strike and for a vertical distance of 1,500 feet. Ore was hoisted from the Anderson mine via a 3-compartment vertical shaft while that of the Brock was brought out by a tram through the main adit. Ore was extracted by a modified room and pillar method with overhead open stopes (Popoff and Service 1965).


The Luke (Mineral Hill) mine is located six miles southeast of the Anderson mine in section 15 T10N, R9W. Prior to the Montana Phosphate Products Co. purchase of the mine in 1943, the mine had produced an estimated 25,000 tons of phosphate rock (Popoff and Service 1965).

Other mines discussed by Popoff and Service (1965) include the Relyea , Gimlet, and Graveley near Garrison and the Bishop and Spokane Chemical Co. prospect on Warm Spring Creek. As with the Anderson and the Luke properties most of the production has been since World War II and has been entirely phosphate rock.


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

Lyden, Charles J.

1948 "The Gold Placers of Montana",

Montana Bureau of Mines and Geology Memoir 26

. Montana School of Mines, Butte. Montana Bureau of Mines n.d. Vertical Files.

Popoff, C. C. and A. L. Service

1965 "An Evaluation of the Western Phosphate Industry and its Resources" Vol. 2. Montana. United States Department of the Interior, Bureau of Mines, Report of Investigations #6611.

Sahinen, Uuno M.

1935 "Mining Districts of Montana", Thesis, Montana School of Mines, Butte.

Wolle, Muriel Sibell


Montana Pay Dirt: A Guide to the Mining Camps of the Treasure State

. Denver: Sage Books.