World's Oldest Known Natural Pearl Discovered; Archaeologists Call ... testimony to the ancient origins of our engagement ...

He says that part of the reason the Marie Antoinette pearl is worth so much is because it's a natural pearl, which brings us to one quality that determines a pearl's value. Natural versus cultured.

Natural pearls are harder to find ... akoya pearls can only grow about 9 or 10 millimeters in diameter, but South Sea pearls and black Tahitian pearls can reach a diameter of around 15 or 16 ...