Support Rock
Either low-grade ore or barren waste rock is suitable for use as GEOCOAT® support rock. Candidates are evaluated for suitability based on the following characteristics:
- Potential for using low-grade ore to add to the metal production
- Physical competency; i.e., resistance to degradation during mechanical handling
- Chemical resistance to the acidic bioleach solutions
- Absence of soluble constituents potentially toxic to the bacteria
- Low carbonate content
- Suitable particle shape and surface characteristics
- Local availability at low cost
An initial supply of about 1.2 to 2 times the annual concentrate tonnage, depending on the number of annual cycles and coating ratio, is crushed, sized, and stockpiled. Since the support rock is reclaimed, recoated with fresh concentrate, and restacked in the heap, only small amounts beyond the initial supply (5% on an annual basis) are needed to make up for degradation losses that occur during each cycle of biooxidation.