The Tahitian Pearl is conceived inside one very particular kind of oyster: pinctada margaritifera var. cumingii. The evocative name margaritifera comes from the Latin word for a pearl. These pearl-bearing oysters are more often called ‘nacres’ (mother of pearl) in French Polynesia, a name which derives from the Persian word nakkar, meaning ‘iridescent.’
Pearl farming or pearl culture has two phases: nacriculture (the cultivation of pearl-bearing oysters) and grafting.
Nacriculture begins during the hot season from November to April. The pearl farmers set up the collectors (also called ‘parasols’) which are made from strips of cloth like awnings hanging from a network of ropes across the lagoons. The collectors are there to encourage the attachment of the planktonic larvae, which have come from the reproduction of the parent molluscs in natural surroundings.
A ‘station’ is a rope on which the collectors are fixed at regular intervals. As collecting is not possible in all the atolls, the pearl-bearing oysters are often transferred from their collection spot to the atolls where they will be grafted.
After six months, the pearl farmer starts the operation called ‘détroquage’, which consists of detaching the young oysters, now called ‘naissains,’ from the collectors.
These young oysters will be pierced on one side near to the hinge, and hung by a nylon thread from ropes called ‘chapelets’ (‘rosaries’ or ‘garlands’). These garlands will carry between 10 and 20 oysters and will be hung from a network of ropes at between 8 and 10 meters depth. The oysters will be regularly cleaned until they reach 10 cm wide, at about 24-36 months old. They will then be ready to be grafted.
Grafting consists of inserting into the oyster a graft and a foreign body in order to make a pearl. This operation requires a suitable area of sea-water, a donor oyster, a receiving oyster, a nucleus (a white bead usually obtained from a freshwater bivalve of the Mississippi, the legumia recta. The size of the nucleus will determine the size of the future pearl), and an expert grafter.
Nowadays, the grafting operation, called ‘the fragment method,’ proceeds in the following way:
- A small fragment or section is cut from the mantle of a donor oyster, this is the graft.
- The right size of nucleus is chosen.
- A receiving oyster is placed on the bench, kept slightly open by means of a piece of wood wedged in near the adductor muscle.
- The pearl sac, which is situated at the end of the animal’s gonad, is incised and the graft and the nucleus are inserted.
– The gonad is anaesthetized to activate healing.
- The piece of wood is removed and the grafted oyster is placed in a tank of sea water.
After 40 days, the grafts will be checked to discover the percentage of success.
The grafted pearl-bearing oysters will remain submerged in the lagoon for about eighteen months, in order to allow the secretion of a layer of pearl which, by regulation, must be of a minimal thickness of 0.8 mm. Throughout this period, the pearl farmer will regularly lift the oysters from the lines to remove parasites from their shells and facilitate the secretion of nacre.
The harvest is the final stage of the process, which consists of extracting the cultured pearl from the pearl sac.