To buy calcium carbonate, you need to know about it first.  A chemical compound with the formula CaCo3, which is mostly found in the form of clay lime and white mud in nature, and its pure form, which is in the form of pure lime, is less found in nature.

  This substance is found in rocks all over the world, and is a major component of the shells of marine organisms, snails, coal balls, pearls, and egg shells.

    Calcium carbonate is the active ingredient in agricultural lime. Calcium ions in hard water react with carbonate ions to form calcium carbonate.

    Sources of natural calcium carbonate can be studied in two ways:
Geologically calcite, aragonite and vaterite: It is a carbonate of pure mineral calcium and is found in nature in three ways:
1-Marble, which is either mined explosively  used as a powder for various industries, or used as a coupe in decorative stones.
2- Limestone
3- Mineral gypsum or travertine
In terms of biological resources: eggshells, snail shells and most oysters are composed of calcium carbonate and can be used as industrial sources.