I don't think that there is any gold there, oil shales were mined around there. Gold prospecting closest to Lithgow would be Sunny corner. You will need State forest fossicing permit.
Karl
Gold has been found near Hartley on the Cox's River. In fact it is thought that one of the first NSW gold discoveries was made there by Reverend W.B Clarke, also a geologist, but kept quiet.
Without researching I would assume that private property might be your biggest hurdle & like Karl says, a State Forest permit & a trip to Sunny Corner or Oberon might be easier to get you started in the area.