RE: Sunday Roast6 Dec 2022 10:14
To elaborate on what I meant by this
>>>It is a a lot easier and cheaper to process the higher grade at a higher economic cut off. As more of the lower grades are now included in the updated JORC, the economic cut off will come down.<
As is shown in the high grade crown of the resource, the 191Mt @ 0.33% CuEq, is reported at a cut-off of 0.2% CuEq. Whereas the overall resource of 512Mt @ 0.22% CuEq*, is reported at a cut-off of 0.1% CuEq.
Cut-off grade depends, upon the processing method used to achieve the best economic productivity. It is cheaper to process higher grades than lower. For example, Milling, which is the cheapest, crushed or agitation leach, and run of mine (ROM) leach. I found that the lowest cut-off grade for milling is 0.18% copper equivalent, for crushed leach 0.12% and for ROM leach 0.05%.
This is so simplistic there are many other factors including dilution of head grade that goes for processing that can affect the cut off too.