All Mikimoto Pearls represent the top 5% of Cultured Pearls harvested. Within that top 5%, the Mikimoto pearl greats are as follows:
AAA: Exceptional Luster, Mirror like reflection, blemish free
AA: Superb Luster, Clear Reflection, Very Slightly Blemished
A+: Very Good Luster, Clear Reflection, Very Slightly Blemished
A: Very Good Luster, Clear Reflection, Very Slightly Blemished
Luster: Luster is the amount of light reflected from the pearl's surface. If refers to both its surface glow and it's "inner light" or deep mirror-like reflection. If nacre quality of the pearl is good, the pearl's overall luster will generally be superior as well. Only the highest quality pearls with the best luster carry the MIKIMOTO name.
Surface: The blemishes and tiny marks found on cultured pearls are produced by particles that brush against the pearl in the cultivation process and are part of the pearl's natural texture. The fewer marks and blemishes a pearl possesses, the higher its quality.
Color: When evaluating color, the two most imporant factors are richness of color and ven color distribution. Pearl colors vary as widely as the types of oyster that produce them. The rarer the shade, the more valuable that pearl tends to be. Ultimately, color is a matter of personal preference... the your choice.
Shape: Although many pearl shapes are available, perfectly round pearls are the rarest and, therefore, the most valuable. The pearls used in MIKIMOTO Akoya cultured pearl strands and jewelry are all concentrically round. With MIKIMOTO South Sea pearls, other shapes like teardrop, oval, button, and baroque are also favored for their uniqueness.
Size: While size does not affect the overall quality of cultured pearls, it does affect their worth. Pearls are measured in diameter increments of millimeters, or mm. Large size pearls, due to their limited availability, tend to be more valuable.