These seven factors affect pearl value: 

1. Size

2. Shape

3. Color

4. Luster

5. Surface Quality

6. Nacre Quality

7. Matching

Size-Size is measured in millimeters. For spherical pearls, measure the diameter; for other shapes, measure the length and width.

Shape-There are three main categories of shape: spherical, symmetrical, and baroque. There are seven standard shapes that fall into these categories.

Color-Pearl color has three components: bodycolor, overtone, and orient.Bodycolor is the overall color of the pearl. Overtone refers to one or more noticeable translucent colors that overlie the bodycolor. Orient is a form of iridescence that appears to be on or just below the surface. Not all pearls display all three characteristics.

Luster-Luster is the light reflected from the surface of the pearl. It's described by its intensity.

Surface Quality-Most pearls have surface characteristics, or irregularities. Surface condition is judged by the size, number, location, visibility, and types of blemishes. Blemishes affect the pearl's appearance; some affect both appearance and durability. Few pearls are completely blemish-free.

Nacre Quality-Nacre quality is determined by its thickness and layering. If the nucleus is visible, the nacre is too thin. A chalky appearance might result from thin nacre or poor nacre layering.

Matching-Matching describes the uniformity of pearls in jewelry. It depends on the consistency of the other six factors. It takes time and inventory to sort and collect pearls for a single strand. That's true even if the pearls are intentionally mismatched. Matching is not a true pearl quality factor, but it does impact value. Matching does not apply to single pearls.