What is Limestone?
How Limestone Forms
Limestone is a relatively soft sedimentary rock composed primarily of calcium carbonate. This chemical compound occurs in rocks as the minerals calcite and aragonite.
Limestone usually forms in clear, calm, warm, shallow bodies of water.
Being so soft, it scratches very easily.
Large quantities of limestone form from the skeletal remains of marine organisms left behind after they die.
The colour of limestone is usually white to off-white. The lustre is dull, meaning the stone's surface absorbs light instead of reflecting it.
Chalk, travertine, and coral are all types of limestone.
Limestone can also form very slowly over millions of years from the evaporation of water in caves. Stalactites and stalagmites form in this way.
Limestone reacts with weak acids, such as vinegar, producing bubbles of carbon dioxide. This reaction is commonly used for identification purposes.
It's widely used in construction, agriculture, and the production of cement and lime.
Article Pictures
The limestone in our first picture comes from Arizona. The second picture is fossiliferous limestone from Indiana. Photos: Courtesy of Stan Celestian.
