Pearl beads: Keishi pearls,also called reborn pearls,keshi pearls Keishi pearls are formed when the mollusk ejects the pearl bead nucleus but continues to make a pearl. The pearl size is refered to its longer length range(e.g. 6-8mm).
A blister pearl (also called a bouton pearl) is a pearl that developed attached to the inside of a mollusk's shell. This type of pearl must be cut off the shell, and is therefore hemispherical.