Limestone is a sedimentary rock. It consists primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. The calcite came from the shells of dead marine organisms, which settled to the sea bottom. Various other constituents, such as silica, clay, silt, sand, organic material, may alter the basic white color and affect other properties of the rock. Limestone is particularly susceptible to dissolution in acid waters, forming potholes, caves, and other depressions.
In the Grand Canyon there are often many fossils of small marine animals sticking partway out of the rock. They can usually be seen easily from the trails. |
