For those interested in numbers here are a couple of observations.
Underground mining in 2019FY cost $79 / tonne of ore.
Over recent years HGO's open pit mining cost was about $15 a BCM of material excavated which is around $6 a tonne.
It seems that an acceptable strip ratio in open pit mining is around 3 to 1.
If an open pit mine can be designed to achieve that sort of strip ratio then mining cost might drop to $24 a tonne.
These savings will be offset by the cost of hauling the ore from Liontown to Thalanga which based on my best guess might be around $30 a tonne so there could be a saving of $ 25 a tonne if open pit 3 to 1 strip mining is possible.
On that basis getting a bit less than half the ore resources out by the open pit method would offset the cost of hauling the other half so a zero sum game overall if that were the case.
If you take the non cash items out of the costs, then it seems that at current prices, positive cash flow can be generated at grades above 9%
