Tokki is a Japanese term to describe a protrusion or bump. Occasionally, oysters will produce a pearl with curious shapes. These are the result of an accident during growth. Oysters definitely have a mind of their own.
There are three different types of Tokki Pearls. The interior may be solid or hollow. The most desirable is the type where the Keshi is adhered to the round cultured pearl. The Keshi part is total nacre and may be separated from the round pearl or as you see in this picture, it is kept in place to create a unique design. The second type occurs when another piece of mantle tissue is floating in the pearl sac and eventually adheres to the bead nucleus, and creates a bubble. The third is a development of two separate pearls in the same pearl sac that adhere to each other and the oyster continues to wrap both pearls in nacre, which ends up looking like a snowman.
As you might imagine, there is no way to organize the end product of an oyster that has made its mind up what she wants to create. Enjoy the Tokki Pearls that you might see and understand that they are a beautiful and unique creation.