On opex, the closest comparison by distance is Sandfire's...

On opex, the closest comparison by distance is Sandfire's operation.... Roughly they're operating at US$1/lb of Copper (on a 5% grade this is approx US$110/tonne).  Extrapolating to lead these costs would have a break even of around 5.5% - Reserve Grade or 6% Resource grade.  What proportion of the mine plan is under 6%?  Of the resources, about 40% of the tonnes fall away when you apply a cut off grade of 6%.  

The biggest area I struggle with this project is on the Capex - the Nova build was A$450m, Sandfire was about $400m - i can't see a similar size build for ~A$150m....