The immense lagoon of the Gambier islands, its low depth and the replacement of the waters by the atoll's openings are critical features for the development of pearl farms. Since the end of the 1960's, Mangarevians have developed farming technics at an industrial level. The Tahiti pearl is based on a specific type of oyster named Pinctada margaritifera. First, oysters are raised (attached in rosaries) in the lagoon for 2 years with a small ball (called nucleus) and a graft inside. Then, the harvesting can take place. At the end of the process, an over-grafting (second operation) can even be attempted.