99.9% of pearls on the market are not natural pearls, but cultured pearls. Cultured pearls are grown by inserting a mother of pearl bead or small piece of oyster inside a particular species of oyster. This object is treated as an irritant inside the oyster, and its natural reaction is to cover the object with a Nacre´ coating. This Nacre´ coating is what is judged when evaluating the quality of cultured pearls. There are five main categories when determining the quality of pearls. The jewelry trade uses these categories to assign a grade for the cultured pearls: AAA, AA, A, and B quality grades, with AAA being the highest quality, descending in quality to B.

The five qualities are:

Luster: Depending on the quality of the pearl's coating, it will display a reflection on the surface. The sharper the reflection, the higher the pearl quality grade.

Symmetry: Pearls are cultured in all shapes from spherical to baroque. In a strand of pearls, the symmetry should be similar throughout the strand.

Color: Pearls display a unique optic characteristic known as orient. This orient is accented by a pearl's body color and overtone. The body color of a pearl is the underlying color of a pearl and is accented by the overtone color. The type and quality of color determines a pearls quality.

Spotting: Due to their growth within the oyster, pearls have surface characteristics that define their quality. Pearls are naturally spotted, and the extent of the spotting determines the quality of the pearl. The less blemishes the surface has, the more brilliant the pearl.

Size: Pearl size is measured in millimeter diameter lengths.