Description:A sedimentary rock formed from calcium carbonate deposited on a shallow, tropical sea-floor. Calcium carbonate is formed as a result of the living processes of plants and animals. In this rock, paler areas contain a proportion of calcium magnesium carbonate (the mineral dolomite). Harder, glassy-looking regions are chert, composed of fine-grained silica that has replaced the original limestone.
Representing:Paleozoic sedimentary rock of Western Canada Sedimentary Basin, deposited in the Mississippian Period, about 340 million
Original location:Exshaw Quarry, Alberta