Protecting Public Health and the Environment.

Gay Mine


The J.R. Simplot Company’s Gay Mine is located on the Fort Hall Indian Reservation, about 16 miles east of Fort Hall, Idaho. It was the only phosphate mine in the southeastern Idaho phosphate field to be located on the Shoshone-Bannock Indian land and was the first open-pit mine in southeastern Idaho to extract federally owned phosphate. The mine eventually consisted of about 7,000 acres of leased Tribal and allottee lands within the reservation.

The Simplot Fertilizer Company (now J.R. Simplot Company) started exploring for phosphate on the Indian Reservation in 1945. The company was established in 1945 to serve regional agricultural markets for phosphate fertilizers. The company’s exploration program consisted of drilling, trenching, sampling and mapping. The exploration proved successful and in 1946, the company negotiated and obtained Tribal and allottee leases on about 7,000 acres (Carter, 1978). The company also obtained a Tribal business lease authorizing it to commence phosphate extraction on February 4, 1946. That same year, the company opened the Gay Mine, which ultimately became the longest operating open pit phosphate mine in Idaho. The Gay Mine was named after J.R. Simplot’s only daughter. The initial production from the Gay Mine marked the beginning of Idaho’s present day phosphate mining/fertilizer industry (Carter 1978).

By the early 1960s, the Gay Mine was producing over 1 million short tons of phosphate rock per year. By the mid-1970s, production approached 2 million tons per year and pit development had extended to the north end of the original lease block.

The J.R. Simplot Company held the majority of the Tribal and allottee leases.  The FMC Corporation held several other leases and the two companies jointly held leases, particularly in the mining area called the “South 40." As noted, a total of about 7,000 acres were held under lease by the two companies; however, only about 2,496 acres were actually mined. In 1990, shortly after the Simplot Company opened its Smoky Canyon Mine and began delivering beneficiated ore in slurry form through a pipeline to its plant in Pocatello, FMC purchased the remaining high-grade ore reserves at the Gay Mine and from that point forward until mine closure total mine production was delivered to FMC.

Along with being the first open-pit phosphate mine in southeastern Idaho to mine federally owned phosphate and being considered as the beginning of the modern phosphate mining era in that part of Idaho, the Gay Mine is also known for another “first.” In August 1980, a D-9 Caterpillar bulldozer operating in Pit CC-3 reduced the limestone footwall that remained above the pit backfill. This was the first highwall removal ever to be done in the southeastern Idaho phosphate field.

After 47 years of more or less continuous production, mining at the Gay Mine finally stopped in September 1993, and all remaining mined ore was shipped.  Reclamation of all of the mine pits open at that time was started in October of that year.

Source: A History of Phosphate Mining in Southeastern Idaho, William H. Lee 2000.