The lichen floras occurring on high-level quartzite, Moine granulite, syenite and calcareous schist in the northern Highlands of Scotland are compared. Rock mineralogy is of overriding importance in determining the assemblages present, though this factor can be modified by extraneous nutrients. Local climatic conditions favour a cloud zone community dominated by ‘alectorioid’ species, produce stony ablation surfaces at a low level and allow maritime species to grow far inland. Ben Hope, with 34 ‘ rare ’ species recorded, is confirmed as a major site for alpine calcicolous lichens. Lecanora chlorophaeodes Nyl., a species new to Britain, is reported from the summit of Ben Loyal. In contrast, the extremely hard, acid, nutrient-deficient quartzite of Foinaven displayed a flora characterized by a very low species diversity.