Limestone is primarily a biogenic sedimentary rock, although under certain environmental conditions abiogenic precipitation of calcium carbonate is thought to occur. The majority of limestone is composed of the broken fragments of skeletal material from animals and calcareous plants. The particles may be as fine as mud (chalk) or may consist almost entirely of pebble sized skeletal plates that may reside within a fine matrix or be cemented by sparry calcite (crinoidal limestone).

 On Arran, the majority of limestone that can be found belongs to the Carboniferous. Repeated fluctuations in relative sea level allowed for the near rhythmic deposition of limestone associated with shale, sandstone, seat earth and coal. Known as Milankovitch cycles, these repeated units of sedimentary rocks record the transgression and regression of the sea with respect to land, and can tell a lot about the environment of deposition due to their abundance of fossils.

Above the road at Corrie Harbor, The Corrie Limestone is exposed in a quarry. The remains of a lime kiln also exist. The limestone was quarried for liming the acidic soils of Arran to improve agriculture. The caves associated with the working are dangerous and should not be entered. Fossils of Gigantoproductus brachiopods can be found in the Corrie Limestone.

Follow this link to find out more about the commercial value of limestone, an important natural resource.