12-14mm Tahitian Black Pearls on Gold Vermeil Leverback Earrings accented with Gold Vermeil Cap. Evaluating the quality of a Tahitian Pearl - color, luster, size, surface quality andshape. Naturally large and round pearls have a higher value than small pearls with irregular shapes. With all other factor being equal, the larger the peal the more valuable it is. Round pearls are the most difficult to culture. The French Polynesian coral crowns in the middle of the great ocean continue to provide the perfect nutritious pristine environment necessary for Tahitian pearl cultivation.