Pearl quality should be judged based on a combination of factors: luster, color, surface cleanliness, size and shape.

Luster is the most important factor as it determines the 'first impression' that we have on a pearl. A lustrous pearl is vibrant, and its surface offers a mirror-like light reflection from within the pearl. Usually a high luster pearl has a thick nacre coating, and the layers of nacre are properly crystallized and well aligned. Japanese Akoya pearls are known for their superior luster; cold water causes the nacre to form slower which contributes to excellent crystallization and nacre quality.

Color may determine the value of a pearl depending on its demand and rarity. While selecting pearls, it is best to choose the color that looks best on you and/or the color you most prefer.

Pearl color refers to the combination of the basic body color and its overtone.

Surface Cleanliness refers to the smoothness of the pearl surface. A perfectly clean surfaced pearl is rare and more expensive. Pearls with slight blemishes cover less than 10% of total surface is considered top grade. Once the pearls are drilled and set, the blemishes are not noticeable.

Slight blemishes are negligible, if there is a budget constraint and/or preferences over size and shape, as long as the pearls are lustrous.

Size The larger the pearls, the more premium on the pearl price. Japanese Akoya pearls range from 2 to 10 millimeters. However, significant price increase is placed on those pearls over 8 millimeter.

South Sea and Tahitian pearls start from 8-9 millimeters and grow up to 20+ millimeters, with the average in the 13-15 millimeter range. While larger pearls are valuable and pricey, they often compromised on other qualities. The longer the pearls stay inside of the mollusks, the higher the risk in increasing surface blemishes and off shape.

Shape The major categories of pearl shapes are: round, semi-round, teardrop, oval, button, ringed/circled, and baroque. The round pearls demand a significant premium as they are most rare and most difficult to grow inside of the mollusks over a long period of time. However, if the symmetry is good, other shapes can be very attractive and interesting as well.