Edible oysters have little pearls more often than one would think. We get a dozen to two dozen from edible oysters each years. That one is large- more like a cherrystone clam.
This is a little off topic, but I can't find the right thread and this is pretty close.The issue is cooking pearls. Edible oysters seem to come through unscathed. It is the pearls from larger quahog (cherrystone?) clams that get mushy when cooked. The porcelain outer surface of the pearl looks OK, but it is soft inside and crumbles easily. But many quahog clambakes are steamed in combo with other seafoods and so, the very rare pearl gets thoroughly cooked.