Cultured pearls are from the oyster family in the ocean or salt water.
Freshwater pearls are from the mussel family and can be found in fresh water like rivers, lakes and ponds. Freshwater pearls are usually smaller, not round, and are much less expensive. Generally, an oyster must be 3 years old before sand can be inserted. Then, usually it takes at least 3 more years to form a beautiful pearl. Larger pearls are more valuable than smaller pearls.