Calcium Carbonate is a common compound otherwise known as limestone. This compound has many uses in medicine, industry, and agriculture. 

The chemical formula for Calcium Carbonate is CaCO₃, the compound consists of Calcium and Carbon Oxide - making it very reactive to water. This compound is found in many forms, the most common ones being: Chalk, Marble, Calcite, Aragonite, and Limestone, as Calcium Carbonate is not terribly reactive with most other materials, it is fairly easy to extract, making massive savings for a mining company. 

Calcium Carbonate Is an Alkali which gives it a place in Agriculture for neutralising soil which is too acidic to harbour crops. The compound can be ground to powder and used like any fertiliser, effectively conditioning the soil. 

There is also a place in Medicine for Calcium Carbonate, it can be used as a source of calcium to treat deficiency, and it can also be prescribed as a very effective treatment for problems with stomach acid. This compound can also be used as a base material for tablets, or phosphate binder. 

The building industry has great need of Calcium Carbonate, some of the most popular construction materials such as Marble and Limestone are originally formed from it. Another huge use of the compound in construction is a filler for certain building materials, including paint and cement, nowadays 30% of paint is composed of either Marble or Chalk. Additionally Calcium Carbonate is used in adhesives and stained glass windows. 

The most known use of Calcium Carbonate is of course in classroom chalk, over 200 tonnes of chalk is distributed around the world every year, not the largest earner of the compound, but certainly a material in high demand. 

Calcium Carbonate has many uses, not only is it a hugely valuable material, but when reacted with other elements it can form other valuable compounds such as Limewater. Unfortunately this compound takes millions of years to form, it is safe to say that we are making the most of it while we have it.