Pearl is nothing else but pearl-shell, arisen in a different way from normal. Pearl is born when an extraneous material gets into the body of the pearl-oyster and the pearl rind around the material can develop spherically inside. Its mild light is caused by the layered, scaly structure, its colours are coming from interference. Usually each pearl-oyster contains one pearl, but rarely two, three or more pearls were found in one pearl-oyster. The weight of pearls is measured in grain.

Its value depends on the shape, colour, brightness and mainly on size. As for the shape, the most valuable ones are the immaculate round shaped and the tesseral pear or drop shaped. In the East people prefer Pearls with a slightly yellowish shade, in Europe and the US the white and the slightly pink versions are more popular.

European people got to know the Pearl later than inhabitants in the East, as there are no pearl-oysters in the Mediterranean Sea. In the Middle Ages Pearl was one of the most appreciated precious stones: symbols of religious and secular power have been decorated with them, like badges, reliquaries, crowns, chalices were decorated with Pearls, besides precious stones.

In the Holy Crown of Hungary, there are 228 pieces of Pearls.

The most precious Pearl is the Southern Cross Pearl, developed from the concrescence of 9 pieces. It was found in 1883, at the coast of western-Australia.

 Mohs: 3.