Keshi, also known as seed pearls, are formed by a loose tissue piece or in a pearl sac where the first generation pearls once grew. They do not contain bead nuclei and are completely freeform.
These fabulous jewels are particularly known for their intriguing shapes and one-of-a-kind attributes. Thanks to their solid thick nacre, they tend to have an incredibly high lustre and a beautiful orient.
Many people have a misconception that these gems are natural. In fact, they are a by-product of the pearl culturing process and are not strictly formed naturally.
Keshi pearls are formed in two ways. After a mollusc is nucleated with a shell bead and a mantle tissue piece, the mollusc may reject the bead or the tissue piece may simply separate from the bead. When this happens, the loose tissue piece might produce a keshi.
They can also form after the first generation pearls are harvested. During the nucleation process, a mollusc is implanted with both a bead nucleus and a mantle tissue piece. When the mollusc secretes nacre, it forms a pearl sac to envelop the bead. After the first generation pearls are harvested, farmers can return the molluscs back to the water to grow second-generation pearls. Keshi can grow subsequently in these existing pearl sacs. They occur in both freshwater and saltwater oysters.