Mabe Pearl (Blister)

Gemstone Name: Blister Pearl aka Mabe Pearl
Found in: Japan
Characteristics: A pearl which formed against the shell instead of in the middle
Hardness: 3
Size: 39x51 mm with a 10 mm thick pearl surrounded by a 3mm thick shell
Polish: excellent
Note - This cabochon is concave - the back is not flat but has a smooth, curved, convex surface and is black with patches of iridescent shell