Sure everyone here has had a good think about this so clarify...

Sure everyone here has had a good think about this so clarify this,

At say 14% DTR, so I guess that estimates the dirt is 14% iron ore (roughly I make an assumption)
good concentrate @ 69.8% earning $ 180 per tonne (not sure where that is paid but I am assuming not at the mine gate)
$180 x 14% says the dirt is worth $25.20 a tonne, less all costs
but you are moving 7.1 tonnes of dirt and processing it to get that 1 tonne of concentrate, and redeposit 6.1 tonnes of spoil

At say 6% DTR, so I guess that estimates the dirt is 6% iron ore (roughly I make an assumption)
good concentrate @ 69.8% earning $ 180 per tonne (not sure where that is paid but I am assuming not at the mine gate
$180 x 6% says the dirt is worth $10.80 a tonne, less all costs
you have to move 16.6 tonnes of dirt to get that 1 tonne of concentrate, and redeposit 15.6 tonnes of spoil

I must have something wrong