Pearl Quality 101 – How GIA Examines and Classifies Pearls
If pearls are your gemstone of choice, you’ll want to learn more about GIA’s 7 Pearl Value Factors™ – the criteria GIA (Gemological Institute of America) uses to classify and describe pearl quality. Read on to learn about how pearl quality is determined and what you can do to find out how your pearls measure up.
Describing Pearl Quality: GIA’s 7 Pearl Value Factors
Pearls come in a wide variety of sizes, shapes, and colors. GIA’s 7 Pearl Value Factors provide a common language to describe them and communicate their quality:
1. Size
The size of round and near-round pearls is expressed in terms of their diameter measured in millimeters. One millimeter is about 1/25 of an inch. Other shapes are measured according to their length/depth and diameter/width.
2. Shape
The three main categories of shape are spherical, symmetrical, and asymmetrical (semi-baroque and baroque). Pearls come in seven basic shapes: round, near-round, button, drop, oval, semi-baroque, and baroque.
3. Color
There are three components: bodycolor (dominant, overall color of the pearl), overtone (one or more translucent colors that lie over the bodycolor), and orient (iridescent rainbow colors that shimmer on or just below a pearl’s surface). Note: not all pearls will exhibit all three characteristics.
4. Luster
Luster is the intensity of light reflected from a pearl’s surface. Luster is one of the factors that give a natural or cultured pearl its unique beauty. Pearls with excellent luster have sharp bright reflections on the surface. Different pearl varieties have different standards for luster. The GIA Luster Scale ranges from Excellent to Poor.
5. Surface
Pearls commonly have blemishes or irregularities that are normally confined to the surface. Surface characteristics are judged by size, number, location, visibility, and the types of blemish. If surface characteristics are numerous or severe, they can affect the durability of a pearl and severely lower its value. They have less effect on the pearl’s beauty and value if they are few in number, or if they are minor enough to be hidden by a drill-hole or mounting. The GIA Surface Scale classifies pearls as Clean, Lightly Spotted, Moderately Spotted, or Heavily Spotted.
6. Nacre Quality
Nacre is the substance that makes up a pearl, layer after layer. Thickness is important when evaluating nacre quality to make sure that cultured pearls are durable as well as beautiful. Nacre thickness measurements are provided as optional descriptions on GIA pearl reports. However, GIA pearl reports will clearly note if the nacre coating is too thin and/or damaged, thereby posing a potential impact on a pearl’s durability. Natural or non-bead cultured pearls with nacre quality issues (damage will also be noted).
7. Matching
This relates to the uniformity of pearls in strands, earrings, or other multiple-pearl jewelry items, and is highly dependent upon a skilled grader to determine matching the other six value factors. The GIA Matching Scale ranges from Excellent to Poor, or listed as Not Applicable for single pearls and certain intentionally mismatched jewelry items.
Each value factor is important in determining a pearl’s overall quality.
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