The purpose of the work described was to compare and contrast the petrography, accessory minerals, and absolute ages of 25 granitic and allied rock samples collected from widely scattered localities in South Australia. The processes that are necessary to be completed in order to produce pure zircon grains for age determinations by the Larsen [U-Pb] method have also yielded concentrations of accessory minerals not normally seen in thin section. These mineral concentrations were subjected to detailed study and comparison by the author, as a basis for his thesis discussions and conclusions. The feasibility of correlating granitic rocks by means of their accessory minerals has been shown to be limited to rocks which are in close proximity to one another. Rocks of the same or similar age but which are widely separated geographically usually show very little resemblance in petrography and accessory minerals. Accessory minerals can most usefully be compared when two adjacent rocks of similar aspect are suspected to belong to different suites and to be magmatically unrelated. The comparisons will usually show whether the adjacent rocks are in fact co-magmatic or not.