Unlike diamonds and other gems or stones, there is no set standard for grading pearls. Each dealer could (and most likely does) have a different standard for their pearl grades. Because of the variation in pearl grading, it is important that each jeweler explain what their grades mean. National Pearl uses the A letter system used by most pearl jewelers to grade pearls. Grading goes from the lowest quality of A to the highest quality of AAA. We also offer the very highest end of the AAA grade in some pearl sizes which we call our "National Treasure Collection". We invite you to compare the quality of our "National Treasure Collection" Akoya Saltwater Pearls with "Hanadama" or Mikimoto brand pearls. Everyone at National Pearl has received pearl grading training from the Gemological Institute of America (G.I.A.). As is their instruction, we grade our pearls on the following factors: Luster: The luster of a pearl is its shine, brilliance, or reflectivity. High quality pearls will have almost a mirror-like reflection, while lower quality pearls appear chalky. Shape: Pearls come in a variety of shapes, from baroque to perfectly round. Rounder pearls hold a higher value in most cases. Surface: Quality 99% of all pearls will have surface imperfections. High quality pearls have very few and are light. These include small surface texture changes and tiny dimples. Very low quality pearls have easily visible flaws that may include deep grooves, holes and cracks. Matching: When making a necklace or bracelet, matching all of the pearls on a strand for all of the factors listed here (luster, shape, surface quality, nacre and color) substantially impacts the jewelry's beauty and value. Nacre:The nacre on a cultured pearl is the natural outer shell that is created by the host oyster or mollusk. Thicker nacre provides for higher luster and longer life. High quality Akoya Saltwater pearls have a nacre thickness of 0.5 to 1.0 millimeters surrounding the implanted bead nucleus.