Size

Factors determining size:
Pearl size depends firstly on the diameter of the nucleus inserted in the gonad during the grafting process; secondly, on the length of the oyster’s gestation period. Their first pearls vary in size from 7 mm to 11 mm, or even larger. During harvesting, another nucleus is introduced, a shell bead of the same diameter as the pearl, and the process of gestation begins all over again until the next harvest. An oyster can endure 3 or even 4 such operations, which are called over grafts by pearl farmers. This results in larger pearls, generally reaching a size of 16mm, in exceptional cases up to 18mm. By this stage, however, the number of high quality pearls produced is very much reduced.

It is worth remembering that Japanese Akoya pearls have a maximum nacre layer thickness of just 0.2 mm and the so-called "South Seas" pearls from Australian are not bound by government regulations relating to minimum layer thickness, thanks to rigorous upstream production checks.