Colour in cultured pearls has many causes, namely organic pigments and the chemistry related to the water reservoir where the pearl shell is grown (for example, sea water and freshwater have different manganese concentrations with impact on the color of the nacre). The pearl mollusc species is, of course, one of the most important factors in this process, specially the donor specimen that provides the mantle tissue graft (known as saibo) that is inserted in the gonads or mantle (depending on the culturing method) of a productive pearl mollusc for the formation of the cultured pearl sac. Experiments in xenotransplantation (meaning graft from one species in host mollusc of another species) have demonstrated that colour is controlled mostly by the genetic characteristics of the graft in cultured pearls.
Furthermore, understanding colour mechanisms is critical in the laboratory to determine if the colour of a pearl is natural or a resulto or a treatment (e.g. dyeing, heat, bleaching).  The pearl oyster Pinctada margaritifera typica has mantle tissue cells that secrete unusual earthy coloured nacre (seen in the oysters' mother-of-pearl shell interior), and thus the colours of those cultured pearls are also expected to be coloured in such a way. 
#southseapearls #tahiti #indonesia #myanmar #pearls #culturedpearls #australia