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Operating the extraction unit.
Safety Inspection of the swing arm for the machinery.
Digging a hole.
Examining the reinforcement beams for placement in the shaft.
Reinforcing the interior walls of the shaft.
Extraction methods.

Mining Process

The platinum group metals (PGM) occur both in primary deposits and placers. The primary deposits are of two main types. The first consists of local concentrations of the metals in olivine-rich rocks, particularly in dunite. Often associated with chromite, native platinum or iridosmine is the principal constituent. The erosion of such deposits has been responsible for the formation of placer deposits of the platinum metals. The most important commercial dunite deposits are in the Ural Mountains of Russia and at the Overwacht in the Transvaal in South Africa.

The second type of primary deposit includes nickel-copper sulphide deposits that are generally associated with norite. These deposits, in which platinum and palladium predominate, make up the greatest known reserves of PGM metals. The most extensive deposits have been found in the norite belt of the Bushveld Igneous Complex in the Transvaal, the Stillwater Complex in Montana, USA, in the Sudbury district of Ontario Canada and the Norilsk Complex in Russia.

Mining Methods

More than 80% of the mining at the Stillwater Mine is mechanized. Mechanized mining costs approximately 40% less than non-mechanized conventional mining methods. The majority of ore produced at the Stillwater Mine is derived from mechanized ramp and fill mining. Other mechanized mining methods also used are sub-level stoping. In areas where the Reef is narrow, Stillwater Mining uses a more selective, less productive method of slusher cut and fill mining to extract ore.

The ramp and fill method begins in a horizontal stope or production level and involves the use of hand held or mechanized drills for blasting and load-haul-dump (LHD) mucking machines to haul away the ore using an access ramp. Advances in the stope are made in 9-foot increments in which ground is artificially supported with rock bolts and other materials. After the stope has been mined out, the stope is then backfilled with waste rock and sand to become the floor for the next horizontal stope, moving upward in 10-foot increments.

Sub-level stoping involves a ramp along the footwall of the reef to allow access to the orebody at 50 foot vertical intervals after which time long hole drilling and blasting methods are used to remove the panel in between the two sublevels. The length of an open section of a sub-level stope may be up to 100 feet along strike and is dictated by presence of ore and/or ground stability. Ore is removed from the open stopes using a remote controlled LHD vehicle.

The mine uses a more selective method of slusher cut and fill mining to extract ore from narrow reef areas. In areas of narrow ore, where the width is 6 feet or less, high-speed machines cannot easily access the reef to extract ore without excessive dilution. Dilution is the amount of waste rock that is removed with the ore. An effective method is for a miner to use a slusher, which is an electric machine with a 48-inch scraper bucket to remove ore from a stope. The bucket is attached to a cable affixed to the face of the stope. The machine is positioned behind the ore chute and pulls the bucket forward, filling it with ore. Cut and fill refers to the mining method of extracting successive horizontal slices from the ore body and then backfilling the void (usually with sand) to form the next working floor.



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