Talc-phengite, an assemblage hitherto believed to be rare, is found in regional distribution in the Gran Paradiso area, where it occurs in the characteristic mineral association chloritoid-talc-phengite (Si3·4–3·5). Talc contains up to 15 mole per cent minnesotaite, and chloritoid up to 45 mole per cent of the magnesium end member. The talc-phengite stability results basically from the disappearance of chlorite + quartz in rocks with low and moderate MgO/FeO ratios through the divariant reactions first recognized here: