The mineralised ore zone at Cattlegrid occurs above a buried land surface of the Pandurra Formation quartzite bedrock. The sulphide mineral depositional sequence shows progressive enrichment in copper at the expense of iron or primary mineralization. In CG Series drillholes the mineralization is zoned in time, with the first-formed primary sulphides being mainly pyrite, carrollite, and possible greigite, which acted as nuclei about which chalcopyrite or bornite later formed. There is the possibility that euhedral quartz and gypsum also acted as nuclei for secondary pyrite precipitation under oxidizing (supergene) conditions. Other metals that have precipitated from the brine-rich meteoric waters have made for a complicated mineralization pattern, mainly in a WNW-trending zone across the Cattlegrid structure. The resulting fine and complex intergrowths of bismuth, lead and zinc minerals with copper sulphides have created problems for mineral dressing. Much of the sulphide ore in vugs and fractures appears to be ensheathed in a film of clay minerals, and this makes for cleaner crushing of the ore, though the clay if not separated complicates flotation of the sulphides. Ore genesis at Cattlegrid is compared with copper sulphide formation in other sandstone environments.