Chemically, pearl grain is mainly a mixture of aragonite and calcite, sometimes with a little valerite added to this mixture. Basically they all consist of calcium carbonate (CaCO3). Mussels living in sea or fresh water use a substance called aragonite that contains calcium carbonate to prevent foreign molecules (mostly grains of sand) from damaging their shells. they are covered with. This substance is known as mother-of-pearl and also covers the inner surface of the oyster. .
Valerit mostly It shows a crystallographic structure with hexagonal symmetry. It is formed by the dehydration of calcium carbonate. By repeating the dissolution-dehydration processes of calcium carbonate, valerite turns into calcite. Calcite biomineralization can be induced by bacteria or, rarely, fungi. While valerite is colorless/bright-looking, calcite can be white, yellow, red, orange, blue-green, brownish, gray. In this way, it is made of calcite and aragonite. A very hard and shiny pearl is formed.