'Black Lip' vs. 'Black-Lipped': Saccostrea echinata

[CortezPearls]

Just read this thread...quite some years after it was posted.
The shell is clearly a Mabe-gai or Pteria penguin shell, sometimes called "black-penguin winged oyster", not because it has a "black" or dark colored nacre lip, but because of the color of its protective protein (periostracum) coloration.

I agree with Jeremy on the edible oyster information...the whole thing was simply a confusion from the jeweler, but the jewelry looks nice.