It is possible that the Riverina has mineral deposits including coal , petroleum , coal seam methane , gypsum , gold , Cobar style polymetallic systems , heavy mineral sands and possibly diamonds in these fold belt rocks and basins . There is potential for the Riverina to host several mineral deposit types including coal , petroleum , coal seam methane , gypsum , orogenic gold , Cobar style polymetallic systems , heavy mineral sands and possibly diamonds in these fold belt rocks and basins .