oxides breakeven

3 Month Copper bottomed at Xmas and has been rising since. From US$3000 to $4,000 today, still on trend. China buying.
Have some recall Oxides economic cutoff was $6500, but that was at higher acid prices. Was that $US or $A?
If its $A and the cost is closer to A$6000 now the current copper price would not be far off that, and trending up.
Price in US up over 3% this trading session, $1.83 lb. All base metals up, copper leading the way. Smooth curve up on 12 month chart.