Ann: Chairman's Address to Shareholders , page-60

Yes, one thing has been forgotten:
PT mentioned at the AGM that the massive stockpile from the 60s or 70s is probably economically infeasible to exploit because different grades were dumped on top of each other so that they really have no idea of how much iron is in there and doing drill holes into the stockpile can't tell them as accurately as when they drill into a consistent ore body.

He said that the grades in the stockpile went as low as 3% or 4%, which is below the exploitable limit, and they don't know where in the stockpile this occurs.