Limestone is a sedimentary rock composed of calcium carbonate (CaCO3). There are various types of limestone, as well as different methods for formation. When limestone is formed through precipitation of water, it is called chemical limestone. When limestone is formed from the shells or skeletons of dead marine organisms, it is called organic limestone. Limestone is soluble, so it is very common in Karst landscapes. Limestone has many uses, but it’s most common use is as a building material for architectural purposes.
Limestone, just like most other sedimentary rocks, is made of grains. The composition of the grains depends on the method of formation of the rock. In organic limestone, the grains are fragments of the skeletons and shells left behind by marine organisms after they have died. These skeletons and shells will often sink to the bottom of the body of water in which they lived, and accumulate on the seabed. Through the process of lithification, the marine organisms’ remains will then form limestone. In addition, this is how fossils are formed. The organisms’ origin is often imprinted into the limestone while it is being formed, allowing us to identify what organism lived in the area, and when it died. For this organic method of formation to occur, a large amount of shellfish, coral, or other marine organisms must be present. It is because of this requirement, that the Bahamas is an ideal location for limestone formation. The seabed in this region is completely covered with skeletons and shells of dead sea creatures.
Limestone can also form inorganically. This method of formation is called chemical, or evaporative. It is through evaporative formation of limestone that stalactites and stalagmites are created. When a cave or cavern has holes or pores in it’s roof, water will flow down through them. If the falling water evaporates before it drops from the ceiling, if this happens, the calcium carbonate that was present inside the water droplet will be...
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