What are Edison pearls?

Two Chinese siblings developed a fresh water pearl that rivals the perfection of Tahitian pearls in symmetry and color. Instead of inserting tissue into mussels as is done with traditional fresh water pearls, they realized that inserting a bead (as it done with saltwater pearls) into the mollulsk triggers it to cover the bead with nacre and form a round, lustrous pearl. And since only one bead is inserted into each shell the resulting pearls are larger than theĀ  usual fresh water pearls. Thomas Edison claimed that the only things he could not create in his lab were diamonds and pearls.