Freshwater pearls are prized for their durability, diversity and their warmth, and above all, their affordability. They are known for their interesting shapes and wide variety of sizes and colors. The character of a freshwater pearl is its distinctive surface texture and luster.
Freshwater pearls are available in a myriad of colors, shapes and sizes. In addition to the traditional white body color, these pearls come in a rainbow of natural colors as brilliant as lavender, peach, mauve, some greys, pinks and every shade in between. Their varied shapes include potato shapes and stick pearls, toothpick, rice shaped and button pearls, coin shaped, square, rectangular, heart and drop pearls, off-round and round pearls.
Freshwater pearls are produced commercially in China (triangle shell and Biwa shell), with the global market overwhelmingly dominated by Chinese pearl producers. Other sources of fresh water pearls are Japan (Biwa pearls and Lake Kusumigaura pearls), as well as the United States (Mississippi River Basin).
Growing of the freshwater pearls is typically by tissue nucleation. The mussels which produce the pearls are surgically implanted with 24 to 32 tiny pieces of mantle tissue, a process known as nucleation. Once they have been nucleated, the mussels protect their flesh from the irritants by secreting nacre, the calcium carbonate compound we know more commonly as mother-of-pearl. Over the course of 2 to 7 years, the mussels deposit layer upon layer of nacre around the growing gems. By the time the pearls are harvested, each mussel has produced more than two dozen pearls clustered on the inside of its mantle tissue.
Drusy pearls are pearls which have a bumpy, pimply surface also found in other gemstones. Only 1% of pearls are formed like this so they are very rare and different.
Keshi pearls, small, roundish, rosebud shaped natural pearls, or petals take 2 to 6 years to develop in the mussel. Perfectly round freshwater pearls are rare.
There are bead nucleated pearls known as furrow or ripple pearls or Chinese Kasumis which have softer glows and more subtle colors.