A narrow band of Index Limestone exposed along the quarry face represents sedimentary bedrock, from shallow carbonate seas. These sedimentary rocks are shallow-marine in origin, the remains of coral and shell fragments, forming beds and locally reefs. They lie below a shallow surface layer of Upper Limestone Formation, sedimentary rocks of fluvial, palustrine and shallow-marine in origin, forming deposits reflecting the channels, floodplains and deltas of a river in a coastal setting (with periodic inundation from the sea). Below the Index Limestone are deeper deposits of Limestone Coal Formation of the Clackmannan Group type.

Crofthead mine appears to have extracted the Index Limestone while Hullerhill Quarry extracts the lower Limestone Coal Formation.