The formation process of cultured pearl is same as that of natural pearl, except in cultured pearl, the human implants the nucleus around which pearl was formed. But in natural pearl, the nucleus is the microscopic intruder or parasite entered by accident.
Basically two types of cultured pearl exist - saltwater cultured pearl and freshwater cultured pearl. South Sea pearl, Tahitian pearl and akoya pearl are saltwater pearls. Almost all freshwater pearls originated from China. More than 80% of akoya pearls also produced in China with the rest from Japan. South Sea pearls are from Australia, Philippines, Burma and Indonesia. Tahitian pearls come from Polynesian islands in South Indian Ocean . Because of rarity, beauty, luster, size, difficulty of farming, limitation of environment, natural disaster, saltwater pearl are more valuable than freshwater pearl under comparable quality. Among saltwater pearls, South Sea pearl commands highest value, Tahitian pearl comes the second. Akoya pearl comes the third. Because of its affordability, excellent luster and consistently round shape, akoya pearls are the most popular pearl jewelry.
Almost all pearl jewelry in the market are made of cultured freshwater/saltwater pearl instead of natural pearl.
Today, "cultured pearl" is still used to describe akoya pearl. Because seller of freshwater pearl may describe as cultured pearl which is not wrong. It is important to know it is freshwater pearl or akoya pearl when seller describe as "cultured pearl" because akoya pearl is much more valuable than freshwater pearl under comparable quality.