Uses
Calcium carbonate has many natural uses as well as commercial ones. The main natural and some of the commercial uses are listed here, but there are many others.
Fossil Records:
Because of the way limestone is formed and the depth at which it is found it can tell a lot about our planet’s history. Chalk deposits and limestone are both made from organism’s calcium carbonate shells, but the organisms that once lived where there are now chalk deposits could only live in shallow water. Thus, chalk deposits in areas indicate shallow water. An interesting discovery that was made by observing that there were large amounts of chalk deposits of the same age on many continents was that this was evidence of world-wide shallow water, which indicates proof for the biblical flood (http://www.amazingdiscoveries.org/fossilrecord2.html). The limestone retains larger parts, sometimes whole shells, of the sea organisms that used to live there. These fossils can also be helpful in telling a story of the earth’s history.
Caves:
Calcium Carbonate is important to the formation of caves, because of its ability to be dissolved by an acid (for more information see behavior/tendencies page). Acidic rain water runs off and goes underground where it dissolves the calcium carbonate limestone. The calcium carbonate water runs down and eventually reaches an air filled cavity underground where the carbon dioxide can be released. When it is released the calcium carbonate crystallizes again, making the cave. The stalactite and stalagmite formations are caused by how the water with calcium carbonate drips, it leaves some mineral at the roof of the cave where it dripped and some where it falls. This is an extremely long process.
Picture of a water drop inside a cave: Picture of a cave in Kartchner Caverns, AZ
Pictures’ Source: http://www.kaet.asu.edu/wildaz/caverns/discovery/discovery8.html
Antacids:
A commercial use of calcium carbonate is its use in antacids. This is also due to its ability to dissolve in acid and to produce carbon dioxide and water. The calcium carbonate in the antacid dissolves in the stomach acid, HCl and produces water, carbon dioxide and calcium chloride. Examples of commercial antacids that use calcium carbonate are TUMS® and Mylanta®
CaCO3(s) + 2HCl (aq) → H2O (l) + CO2 (g) + CaCl2
Paper Industry:
Calcium carbonate in the form of chalk is used as filler in the paper industry. It is used as a cheap way to make bright opaque paper (http://www4.ncsu.edu:8030/~hubbe/CARB.htm). Filler is used at the wet-end of paper making machines, the calcium carbonate filler allows for the paper to be bright and smooth.
Construction Industry:
Limestone is used in decorating and construction as well as its heated form, marble, but there are other construction uses for limestone and calcium carbonate. The main one being its contribution to the making of mortar which is used in bonding bricks, concrete blocks, stones, and tiles in construction.
Glass Industry:
Limestone is added to glass because it has low water solubility.
Steel Industry:
Limestone is used to collect any impurities that might be in the steel materials.
Lime:
Lime is CaO and is useful in many industrial areas such as the steel industry, the refining of gases, the paper industry, the glass industry, and refining sugar. Calcium carbonate decomposes to form lime and carbon dioxide.
Calcium Carbonate at the Grocery Store:
Calcium Carbonate is found in many grocery store products such as backing powder, dry-mix dessert mixes, dough, plastic, and wine.
Optics:
Calcite’s property of double refraction is useful in the field of optics. In the late 17th century Erasmus Bartholinus discovered the double refraction property in calcite crystals. This property was discovered to be able to be used to polarize light as a prism. Polarized light is used in optical filters and to identify crystals and optically active compounds. It is also used in optical instrument such as polarizing microscopes and Nicol prisms. The Iceland Spar calcite crystals are usually the ones used, since it has the right properties for the double refraction. Nicol prisms are used in microscopes. (For more info about double refraction see behavior page)