Say China spits the dummy and refuses to buy any Australian iron ore it will be no skin off our miners' noses (assuming that China continues to buy as much iron ore as they would have from us). Say they buy exclusively from Brazil. If they do that then other buyers like Korea and Japan will be pushed out of the Brazilian market and will buy more from the Australian mines. Same demand and same supply should mean same prices.
It is the same logic as for Iran not selling oil to the US. As long as Iran keeps supplying the stuff to the open market and the US keeps buying the stuff on the open market then prices are not affected by the fact that Iran does not sell directly to the US.
What would change things is if China worked out how to get iron ore for cheaper than what they pay for Australian iron ore. An example of that is how they started using pig iron nickel to undercut our nickel laterite miners.
But imo bottom line is that they need us and we need them.
