Why is it that pearls are something very special for most of us? It’s not a question for scientific discourse. The delicate look, the spherical form, and the lustrous surface of the pearl – as well as the fact that the origin of this perfect shape is natural – give a piece of jewellery with pearls a value that exceeds the tangible value. Rare natural pearls occur in freshwater as well as saltwater mussels under circumstances that are not fully understood yet (astonishing in today’s thoroughly rationalised world) when a concentrated development of nacre is prompted.