The mining licence application for the Bylong Valley between Mudgee and Denman was recently rejected.
How did that rock get there, fuck knows?
A couple of ways. If there was glaciation in the past- and Australia was further south in the Jurassic/Cretaceous - and volcanic activity.
Glaciers move slowly, and drag everything with them, including large rocks. When they melt, they leave the rocks behind. They can also carry them out in huge icebergs, which melt and release the rocks onto the ocean floor. The rocks come to the surface when the ancient seas recede. The term is called "drop stones".
The other way is that there were lots of rocks thrown out by volcanic eruptions, and the softer ejects have weathered away, leaving the harder parts as orphans.