Stillwater Mining is proceeding with two mine resource delineation and development projects along the Stillwater Complex at its mining operations in southern Montana. Both projects lie within the boundaries of existing mining permits, and each will initially be serviced from existing mine infrastructure.
The Graham Creek project will probe the Stillwater Complex immediately to the west of the company’s East Boulder mine, while the Blitz project will undertake a similar task to the east of its Stillwater mine. Based on indications from historical surface delineation drilling in these areas, the company views both projects as having a high probability of significantly adding to its probable platinum group metals (PGM) reserves.
Over the next several years, the Graham Creek project aims to extend the East Boulder mine ore resource about 7,900 ft further west, on the far western end of the Stillwater Complex. East Boulder’s tunnel boring machine (TBM), which was used about a decade ago to develop initial access to the JM reef and then to develop the footwall lateral that parallels the reef, has recently been re-commissioned for the new project. Initial work will assess reef continuity and structural controls in this area of the reef. Based upon historical surface drilling and production experience at East Boulder, the project has the potential, over time, to develop up to 6 million additional st of ore grading on the order of 0.41 in-situ PGM oz/st.
Once the initial Graham Creek development is completed, any future mining in the area would require adding ventilation raises and additional infrastructure prior to beginning ore production. Costs to complete the TBM development drive and assess the PGM resource for the Graham Creek area are projected at about $8 million over the next five years. The project is expected to yield information on the Graham Creek resource as diamond drilling work is completed behind the TBM drive.
The Blitz project at the Stillwater mine is designed to explore and define the PGM resource along the far eastern extent of the JM reef. It will extend some 13,500 ft to the east of the existing Stillwater mine via two conventionally driven footwall laterals from the mine’s 5000 and 5600 levels. Diamond drilling and geologic evaluation will be concurrent with footwall lateral advance on both levels.
Once the Blitz assessment project is completed, additional development will require excavating new ventilation raises to support bulk sampling, final pre-production development and eventual ore production. Based upon production experience to date and historical surface drilling, Stillwater believes the project has the potential to define up to 9.5 million additional st of resource grading on the order of 0.71 PGM oz/st. The project will begin to yield resource results within its first couple of years. Initial development and resource evaluation costs for the Blitz area are expected to total about $60 million over the next five or six years.