Understanding the Chemical Composition of Limestone

Limestones are sedimentary rocks made of calcium carbonate, a chemical compound containing three elements: carbon, oxygen and calcium. Limestone is widely used as a building material, as well as an ingredient for making lime, cement and glass. Powdered limestone can be used to neutralize the acidity in lakes and soils.

Calcium

• Calcium is alkaline, silvery-white in color, and occupies the 13th position in the list of most common elements in the universe. Over time, water percolating through limestone rocks can form stalactites and stalagmites, which are often found in caves. This happens because the water dissolves the calcium, which gradually accumulates to form long shapes on the ceiling and ground of caves.

Carbon

• Carbon is found in nature as a free element, as graphite, in diamonds and in fullerines. However, the element is more abundant as a compound, such as carbon dioxide, and is a component of rocks in the form of carbonates of calcium, magnesium, and iron. According to Los Alamos National Laboratory, there are almost ten million known carbon compounds. Some of the most important compounds of carbon are carbon monoxide, carbon disulfide, methane, ethylene and carbon dioxide.

Oxygen

• Oxygen is a very reactive gas, forming compounds with most elements. Oxygen is the third most abundant element in the sun and forms 21 percent of the Earth's atmosphere. Oxygen and its compounds constitute 49.2 percent by weight of the Earth's crust, reports Los Alamos National Laboratory. In limestone, three atoms of oxygen are linked to a carbon atom to form an ionic carbonate.