Radio Hill and Sholl Heap Leaching Project

The Radio Hill mine, located 35km south of Karratha, produced nickel and copper concentrate for four years, before being placed on care and maintenance in 2008 following adverse movements in commodity prices. The Company has recently finalised a detailed Scoping Study which outlines how the mining operation can recommence using a bacterial heap leaching process to deliver project revenues of $815 million over the initial nine year mine life. Fox plans to mine an inventory of six million tonnes of mineralization containing weighted average grades of 0.59% nickel and 0.79% copper. The heap leaching operation is expected to have a Net Present Value (NPV) of $73 million (8% discount rate), an Internal Rate of Return (IRR) of 31% and a net operating cash flow of $125 million.

The utilisation of heap leaching for metal extraction at Radio Hill saves the Company power costs and yields higher metal recoveries than the conventional crush, grind, and float process. In addition, the end sale-product contains a much higher metal content (and hence, higher value) than conventional concentrate material. The reduction in product volume also reduces handling and transport costs.

The existence of established infrastructure including granted mining leases, operating licences, offices, buildings, accommodation, underground mine, tailings dam, grid power, mains water and roads will result in a rapid project ramp-up, lower start-up capital costs and lower ongoing operating costs.

At least one third of the ore feed for the initial year of production at Radio Hill will be derived from existing surface stockpiles (approximately 300,000 tonnes), representing a significant saving in mining costs and leading to further cost savings for the project.

The Radio Hill and Sholl operations will process ore within a range of 400,000 - 850,000 tonnes per annum and will be operated in two phases. Phase 1 will involve processing Radio Hill ore that is on surface and from the underground mine. Phase 2 will involve leaching disseminated ore that will be mined from Sholl B2, B1 and A1.

Exploration continues in the regional vicinity of Radio Hill with the possibility of further extending the life of mine.

Bacterial Heap Leaching

The process of heap leaching has been used since the mid 20th century, particularly to extract gold and copper from low-grade oxide ores. Mined ore is crushed and heaped on an impermeable plastic and/or clay lined leach pad where it can be irrigated with a leach solution to dissolve the valuable metals. The solution is percolated through the heap and collected in a pond before progressing to a metal recovery process.

The nature of the irrigation solution depends on the ore being leached. The ore at the Radio Hill and Sholl deposits is disseminated sulphide ore and therefore requires bacterial action to oxidise the ores and release the associated base metals. 

Sprinklers, or more often drip irrigation, are used to deliver the leach solution to the heaps. The solution then percolates through the heap taking any metals released through bacterial action into the solution as it progresses. The pregnant liquor solution (PLS) containing the dissolved metals is then collected and delivered to the process plant where the metal is recovered from the PLS.

Downstream processing of the PLS then manipulates the chemistry of the PLS in order to remove contaminants and produce relatively pure separate base metal products.  In the Fox Heap Leach Project, iron is removed from the solution and then a copper sulphide and mixed nickel/cobalt sulphide is precipitated from the solution via sulphidization.Replica Rolex

 

Radio Hill Processing Route

 

Radio Hill Processing Route