When Blackham completed an expansion pre-feasibility study on Wiluna last year it found a significant proportion of oxide and transitional probable reserves.
That PFS had assumed the transitional ores would have to be processed through the sulphide circuit - a mix of flotation and a Biox plant.
Testwork has since showed those ores are better served being treated through the existing CIL plant.
Indeed, not only do the transitional ores get better recoveries through the CIL plant, the processing cost is about 30% less than the sulphide plant.
Average leach recoveries on the oxide ores were 90.8% after 24 hours with little increase in recovery after that.
Bond ball mill work index tests on the oxide ore range from 10 kilowatt hours per tonne to 14kWh/t.
Gravity gold recoveries only ranged from 1.3% to 9.8%.
Cyanide consumption results were low to moderate, ranging from 0.14 kilograms per tonne to 0.23kg/t over 24 hours.
Lime consumptions were low range from 0.6kg/t to 14.kg/t over 24 hours.
Average leach recoveries on the transitional ores were 84.3%.
Cyanide consumption results were 0.14kg/t to .2kg/t over 24 hours and lime consumptions were 0.7kg/t to 1.3kg/t over the same period.
Bond ball mill work index tests on the transitional ore range from 16kWh/t to 19kWh/t.
Blackham is re-estimating the open pit free milling resources and reserves around the Wiluna mine site.
