What are pearls actually made of? In general, it can be said that it consists of a kind of spherical accumulation of mother-of-pearl, or a mixture of aragonite ("carbonate of lime") and conchin, an organic horny substance.
Pearls are ultimately created by the fact that mussels and snails produce the pearls out of a protective reaction. However, only very few mussel and snail species form pearls. Most of these pearl-like structures are not made of mother-of-pearl, but of a porcelain-like, calcareous, often blunt substance that is similar to the shell material of mussels and snails. In comparison, however, there is a pearl oyster of the genus "Pinctada", which forms pearls of iridescent mother-of-pearl. The nice thing about it is that depending on the influence of the light, the material appears in a different color. For this reason, these oysters are also considered the most famous supplier of pearls.
Pearl oysters are found on mussel beds near the Atlantic and Pacific coasts at depths of 15 to 20 meters. To defend themselves against parasites and foreign objects entering the animal, the pearl oysters form pearls. So far the common thesis. However, this one foreign body alone is not enough for the mussel to form a pearl.
A piece of the sheath fabric is decisive for the formation of pearls. This piece sits directly under the mussel shell and must penetrate the interior of the mussel with the foreign body in order to trigger the formation of mother-of-pearl. Only the said mantle tissue has the effect that the penetrated body is repeatedly covered with layers of mother-of-pearl. This process kills the foreign body and ensures that the mussel is no longer threatened by the intruder.
