@insaf@redned71I agree with the sentiment of both of your posts. However, I would like to clarify my understanding of the math.
Redned71, you said "for those not clear on this, let’s take 100 tons of ore in ground. Let’s use 20% for this example. After they concentrate it, it will be a maximum of 20 tons of high grade concentrate produced. "
I thought that 100 tons at 20% would contain 20 tons of Fe material. Therefore, 28.5 tons of an end product at 70% could be produced from 100 tons at 70% (28.5 tons at 70% would contain 20 tons of Fe material).
Therefore, to calculate the tons of end product, the math would be resource tons multiplied by head grade Fe% divided by end product Fe%. (this ignores anything lost in production, but provides an indication)