you just need to look at the historic gold recoveries at Hillgrove - 35%-50% on refractory and even lower on antimony.
http://www.redriverresources.com.au/operations/hillgrove/hillgrove.htmlthese are very low recoveries, but not unusual for refractory ore.
why are they so low? Because there's no single process recovery for these ores. Sometimes it takes roasting or bio-oxidation, sometimes autoclave is required. How do you know if the roasting is useful or harmful to the refractory gold, or bio oxidation helpful? Or maybe the autoclave is better? You don't know until you test it, and therefore many tests are required and $$$$ spent until the exact flowsheet is designed.
It is necessary to answer these metallurgy questions, and I haphazard a guess that neither strait resources nor bracken resources cracked the code despite spending hundreds of millions. Why did Emu NL pull out of the deal back in 2012?
If processing refractory gold was that simple, then there will be one universal and simple flowsheet with high recovery.
