The Gay Mine is located on the Fort Hall Reservation. It is one of 31 phosphate ore mines in the Southeast Idaho Phosphate Resource Area. Originally named after Gay Simplot, the daughter of J.R. Simplot, the Gay Mine came into existence in 1946 to supply phosphate ore to the J.R. Simplot Company (Simplot) fertilizer plant in Pocatello. FMC Corporation (FMC) received ore under an ore supply agreement from 1948 to 1993.
The Gay Mine consists of a series of phosphate ore deposits mined by the J.R. Simplot Company from 1946 to 1993, when the Gay Mine ceased operations. The Gay Mine was operated under mineral and business leases between the Shoshone-Bannock Tribes (Tribes) and individual Tribal members (allottees) as lessors, and the J.R. Simplot and FMC as lessees. Simplot held the majority of the Gay Mine leases, and FMC entered into leases beginning in 1956. In 2003, the Bureau of Indian Affairs (BIA) issued a determination that the Gay Mine mineral leases had expired of their own terms. Over the life of the mine, FMC and Simplot paid approximately $60 million in royalties and rent to the Tribes and Tribal landowners for the extraction of ore from the Gay Mine. The Gay Mine was a source of employment for many Tribal members.