Pearl Culturing
Natural pearls are pearls produced naturally without any human intervention, while cultured pearls are pearls produced with or without the insertion by man of a bead by grafting, followed by maintaining the mollusk in culture until the pearl is harvested.
Most of the genuine pearls available in jewelry stores are cultured—which means they were grown on a pearl farm. Pearl farms can be set up in rivers, lakes, or oceans, depending on whether you want to grow freshwater or saltwater pearls. To grow properly, oysters and mollusks need clear, tranquil waters at a temperature of about 20-30º C (or about 68-86º F).
Pearl farm oysters and mollusks can be bred in captivity or collected from nature. When an oyster or mollusk is between 2 and 2.5 years old, it is ready to be implanted with a tiny bead that will grow into a pearl. The implanting process involves special technology that ensures a high survival rate.
After they have been implanted, it will take an oyster or mollusk 2 to 3 years to produce a pearl. Winter is the best season for pearl harvesting, because pearls tend to have a deeper luster at this time of year. Before the pearls are sold, they go through a process of sorting, cleaning, bleaching, and polishing to prepare them for the market.

Freshwater pearl culturing
Mother of pearls
Hyriopsis cumingii, Hyriopsis schlegeli, Cristaria plicata
Growth Environment
Freshwater
Region
Lake, river, pond
Nucleus
With small or without nucleus
The inserted nucleus is a membranous tissue of mollusks

Saltwater pearl culturing
Mother of pearls
Pinctada fucata, Pinctada imbricate, Pinctada maculate, Pinctada margaritifera, Pinctada maxima, Pinctada mazatlanica, Pinctada radiate

Growth Environment
Saltwater
Region
Wide distributed in different region of ocean
Nucleus
With large nuclei of mother-of-pearls bead, plastic bead