Lustrous Tahitian Pearl and London Blue Topaz 16 Sterling Silver Necklacewith a Lobster Clasp 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.