Pearl grading is a system used to evaluate the quality and value of pearls based on several factors: Luster: This is the amount and quality of light that reflects off the surface of a pearl. Higher luster pearls are more valuable. Surface: This factor refers to the cleanliness or smoothness of a pearl's exterior. The fewer blemishes or irregularities, the higher the pearl's grade. Shape: Round pearls are the most coveted and thus receive the highest grades. However, other shapes like teardrop, oval, or baroque can also be appealing and valuable. Color: While this is often a matter of personal preference, some colors are rarer and more sought after than others. Size: Generally, larger pearls command higher prices, provided they maintain good scores in the other grading categories. Nacre thickness: This is particularly important for cultured pearls. The thicker the nacre (the substance pearls are made of), the longer the pearl will last and the richer its luster will be. Different systems are used worldwide, but AAA-A is one common method, with AAA being the highest quality.