More rare than white pearls, black pearls come from the giant black-lipped oyster called the Pinctada Margaritifera. These iridescent pearls range in colour from deep midnight black to shimmering emerald green and pale silver blue. Although black pearls are found in various oceans around the world, Tahitian black pearls are particularly renowned for their sheen and beauty. Tahitian pearls are usually graded on an A to D scale.