Locality 

The pilot for this project would be the Limpopo Provincial Government owned Dilokong Chrome Mine, 30 km north of Burgersfort on the farm Mooihoek 255 KT. Once the extraction by a mobile plant has proved successful, the project can be extended, with agreement from the relevant rights holders, to other chrome mines in the Eastern Bushveld.

Background

The project is based on detailed sampling that was carried out on the Dilokong tailings dump in early 1990s that yielded average grades of 4 g/t platinum group metals and gold (PGM+Au). Subsequent work carried out by Mintek showed that a concentrate could be prepared with 230 g/t PGM + Au and 79% recovery. However, as the concentrate still contained 7.5% chromite, no PGM producer would toll smelt/refine the concentrate at that time. With the current price of platinum above US$ 500 per ounce, such grades are highly viable, in fact Goldfields are investing heavily in exploration of prospects in Finland with PGM contents as low as 1.78 g/t to 3.5 g/t. The only problem at the time of the initial investigation (early 1990s) was the excessive chrome content in the concentrate, an issue which we believe has subsequently been resolved in efforts to use the chrome-rich UG2 ore horizon as ore, and other Mintek initiatives.

We feel the time is ripe for this project to be implemented and though it is initially a focused project (which we see as a positive attribute), it could be expanded to all other LG6 chrome tailings dumps, which between them hold millions of tons of tailings.

Geology

The LG6 chromite seam in the Eastern Bushveld Complex is mined for its chromite content. Although PGM+Au occur in sub-economic grades in the in situ chromite, the chromite processing techniques tend to concentrate PGM+Au into the waste tailings at economic grades. The mechanisms of the PGM+Au upgrade and reasons for the erratic nature of the PGM+Au content are not known.

Proposal

Mintek would be a leading agency in this project to produce a financial and technical feasibility study for the erection of a small, mobile PGM+Au concentration plant at Dilokong to rework chromite tailings with the concentrate being toll smelted and refined using latest Mintek technology. Pilot plant studies previously conducted by Mintek were successful. Geoscience could assist in more comprehensive re sampling of the dumps if money were made available and the cost estimates given below are made only for this latter reserve and grade evaluation exercise and exclude beneficiation test work and plant design.

Outcome

There would be associated employment, but the biggest factor would be potentially high-income returns that, in the case of Dilokong, could be used for other small-scale mining projects or set up a small-scale mining school. At the same time, the project could be used to rehabilitate the tailings dumps, either introducing the tailings back down old workings as backfill or onto more environmentally friendly re-engineered dumps.

Preliminary costing for reserve estimation only:

References

Loo, J.P., 1988. Recovery of Platinum Group Metals from Dilokong Chrome Slimes, Mintek Comm. No. C1005M

Burger, A.J.,  1989. Recovery of Platinum Group Metals from Dilokong Chrome Slimes during 70 hours of continuous flotation. Mintek Comm. No. C1244M.