Cultured pearls start their existence by the introduction of an irritant into a mollusc by man, after which the process is continued solely by the metabolism of the living mollusc. Once the technician implants the irritant bead into a pearl bearing mollusc adding a graft made from epithelial cells the process can begin, in this case, it is not so much “make a pearl or DIE” as we read within the natural pearl formation, but more an alleviation of the discomfort created by the graft and irritant for the mollusc, it cooperates and creates the beautiful lustrous orb that is a pearl.
The crucial role of epithelial cells
The sole role in life for an epithelial cell is to make nacre, (calcium carbonate and Aragonite) this is normally laid in layers on the interior of the shell in order to create a hard surface – or natural armour -making it crunchy and less attractive as a meal for predators, the same nacre substance is laid in concentric layers on the irritant which in effect entombs it. Oysters create two layers of nacre each tide, however each layer is super thin hence although a cultured pearl may only be formed within three years in a farm it literally has thousands of layers of nacre.
Where do the Epithelial cells for a graft come from? In a cultured pearl the epithelial cell graft comes from the mantle tissue of a donor mollusc, which has been chosen for its extra beautiful shell colouring and markings. The donor is sacrificed, and its mantle is cut up into small segments, each segment is then placed into the “surrogate” mother mollusc.
Pearls and human embryos are remarkably similar The graft which has been placed in the “surrogate mother” mollusc forms a pearl sac that covers the irritant and within this sac the mollusc will secrete concentric layers of nacre to cover the irritant. The pearl then rotates within the pearl sac, and as it rotates more layers are deposited onto the irritant. So as a human embryo moves around in the placenta as it grows so does a pearl during its formation.
Pearl bearing molluscs have a mind of their own ! It is important to bear in mind that after the irritant has been introduced the process is continued solely by the metabolism of the living mollusc. The pearl farmer has no control over what the pearl bearing molluscs will produce whether in size, shape, colour, or even whether they will produce a pearl at all. Each pearl is truly individual.
Did you know there are two main types of Cultured pearls? there are seawater or freshwater cultured pearls just as in the natural pearl realm, to learn more tune into our next episode of Cultured pearls.