Chalk

Chalk is a loose, earthy form of calcite or limestone. Its main chemical component is CaCO₃, and its primary mineral is biological micrite calcite. In purer chalk, the calcite content can exceed 99%. It often contains impurities like quartz, feldspar, clay minerals, and sea green stone.

Based on its color and how well it’s cemented, chalk is divided into four types: white chalk (with a CaCO₃ content of 99%), marl chalk, chalk-like limestone, and glauconite chalk.

Chalk is white and disperses easily. Its particles are round, fragile, and absorb little water. It has weak cementation, crushes easily, and offers excellent coating ability. Chalk is used broadly across industries such as rubber, paper, paint, plastics, pigments, coatings, ceramics, sugar, casting, and also in products like grease and sealants.