Talc occurs in the Mount Fitton area in a massive recrystallized dolomite of Proterozoic age. The larger talc deposits are concentrated on its margins. This massive dolomite cuts through bedding and formation boundaries, and available evidence suggests that it was originally a limestone reef. The dolomite is much affected by shearing, whilst the overlying less competent beds have been folded. Talc occurrences are invariably connected with shear zones and shear faults. A combination of metasomatic and structural processes seems to be the most likely explanation of the features observed. Under this concept, talc would be formed where shearing has weakened the rock and opened the path for metasomatic replacements, and the amount of talc deposited would depend largely on the amount and intensity of shearing. Tremolite, which is widespread throughout the whole dolomite and occurs in talc lenses too, was probably formed well before the talc as a product of general metamorphism.