This report is intended to be a convenient single reference to the Cattlegrid ore deposit geology. It represents an updated summary of a large amount of data, gleaned largely from internal company reports. The subject matter relates mainly to the geology of the mine pit area, but the report also includes sections on regional setting, deposit evaluation and ore reserves. Exploration research aspects, mill production reports and ore concentrate output shipping summaries are also included. The orebody is a concealed, sandstone-hosted copper (-zinc-lead) sulphide deposit with an economically significant silver content. The stratiform mineralisation is hosted primarily by a localised closely-fractured and brecciated zone developed about the disconformity between the Pandurra Formation and Whyalla Sandstone, and its margins extend upwards and downwards into these units. The breccia zone is considered to be part of a palaeo-weathering profile, of palaeo-permafrost origin. The source of the copper metal is considered to be the pre-Adelaidean volcanic basement. At Cattlegrid, it has been found that copper is the best geochemical indicator, and that IP surveys have proven to be the best geophysical indicator, to buried mineralisation. Within the orebody the assemblage of minerals that has been identified comprises pyrite, marcasite, arseniferous pyrite, carrollite, sphalerite, chalcopyrite, bornite, digenite, djurleite, chalcocite, galena, wittichenite and native bismuth.