Freshwater pearls are grown in freshwater mollusks found in lakes, ponds, and rivers. Today, freshwater pearls are grown on pearl farms found in many countries.

Most freshwater pearls don’t require an irritant, called a nucleus, for production. Rather, a tissue graft from the mantel of the mollusk begins the process. Freshwater pearls are almost completely without a nacre. As such, they do not produce near the luster of saltwater pearls and hence are not near as valuable. However, some freshwater pearls from Tennessee are produced like saltwater pearls and do contain a nucleus.

American freshwater pearls are allowed to mature for much longer than other cultured pearls - up to 5 years, compared to 1 year for most other pearls. The longer the growth, the thicker the nacre. As such, American pearls have an unusually high luster.

Each freshwater mussel can yield up to 30 pearls per harvest as opposed to saltwater mollusks, which produce only a single pearl. Freshwater pearls are available in a far wider color range than saltwater pearls, including purple, violet, orange, blue and gray. Freshwater pearls are generally smaller in size than saltwater pearls.

Lake Biwa in Japan has long been known as the king of freshwater pearls, to such an extent that Biwa has become synonymous with freshwater pearls. But Lake Biwa is polluted and somewhat dried up, so finding authentic Biwa pearls from Lake Biwa is very difficult today.

Due to their high quality and low price, freshwater pearls are a popular choice in pearl jewelry and much in demand. Saltwater pearls are somewhat rare and demand a higher price over their freshwater cousins. This is why saltwater pearl jewelry is often more expensive.