A cultured pearl originally non-nucleated, grown in a freshwater mussel from Lake Biwa in Japan. Only those actually produced there should be called Biwas; others are simply called freshwater cultured pearls.
A freshwater pearl grown in lake Biwi in Japan Black pearls Blister
A biwa () is a Japanese short-necked fretted lute, and a close variant of the Chinese pipa. The biwa is the chosen instrument of Benten, the White Snake Goddess of Japan's Shinto religion.