Two cost variables critical to the economics of every ICD deposit are RE recovery to product and the the leach cost involved. Low recoveries = uneconomic, very high leach cost with good recoveries = uneconomic etc.
Initial 'Weak Aqua Regia' (WAR) digest lab assays are only 'weak' by reference to strong AR, not weak compared to just a 0.5M ammonia salt solution at neutral pH and room temperature for example. Good recoveries using very cheap leach liquor on crude leach heaps is the holy grail and what many Chinese ICD's employ to extract REO from ore.
That Leach test list you posted covers the main variables that effect leach recoveries, and obviously cost for each variable across the range of possible inputs. To crack monazite for example requires concentrated sulphuric acid heated to ~2050degC and low wt% solids to liquid... not cheap. Acid pH <1 requiring lots of expensive acid consumption won't cut it for very low grade clay hosted deposits. The outcome of ANSTO's tests are critical to the potential economics of Mt Clere... could be they get same high recoveries from just 0.5M ammonia salt as with the WAR from the lab, don;t know until you test it.
Think I posted this link before, good simple read on description of RE extraction from ICD deposits.
| http://www.eurare.org/docs/eres2014/seventhSession/SebastiaanPeelman.pdf |
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GLTAH
