The group largely comprises limestones, including biosparite and cherty micrite but also some subordinate mudstones, siltstones and dolomites.
Basaltic lava and sills are also found, together with tuffs and volcanic breccia.
Its base is generally an unconformity on lower Palaeozoic rocks though rests conformably on Devonian to Carboniferous anhydrites and dolomites in places.
Over 14 agglomerate vents have been identified in the Peak District along with 30 individual lavas.
Where the proportion of igneous rocks within the Peak Limestone increases to the east, these strata are identified as the Fallgate Volcanic Formation as in the inlier at Ashover.