How Does the Gemological Institute of America or GIA Grade Pearls?

Pearls are graded based on factors like size, luster, shape, and more.

If you've ever purchased a diamond for an engagement ring or other piece of meaningful jewelry, you may have heard of the Gemological Institute of America or GIA. Founded in 1931, the GIA is a nonprofit institute that's dedicated to education and research in gemology and jewelry arts.

In an effort to protect jewelry buyers and create transparency in the jewelry industry, the GIA sets and maintains the standards used to evaluate gemstone quality. A GIA-certified diamond, for example, is graded for cut, color, clarity, and carat weight or the "4 Cs". GIA isn't the only gemstone-certifying organization, but it's one of the most respected in the industry.

Did you know that the GIA also grades pearls? After a 60-year period of researching pearls, the GIA developed the 7 Pearl Value Factors, which is a trademarked system that can evaluate all types of pearls and describe their quality in an easy-to-understand way. Unlike diamonds, pearls are graded for Size, Shape, Color, Nacre, Luster, Surface, and Matching.

No one factor is more important than the other, and a pearl's value is determined by how well all the factors work together in the single pearl. In this blog post, we'll explain how the GIA goes about grading each one of these qualities and why they matter, so you can keep them in mind when purchasing a custom pearl necklace.


Size is self-explanatory. A large pearl is not automatically more valuable than a small pearl, but a large pearl that demonstrates exceptional value factors will be more valuable than a small pearl with equal value factors.


Did you know that pearls actually come in seven shapes? These include round, near-round, button, drop, oval, semi-baroque, and baroque. When a grader is evaluating a pearl for shape, he or she will consider the pearl type. For cultured pearls, round is the most rare shape, since it's so difficult to culture, and Japanese saltwater cultured pearls are held to the strictest standards for shape. However, a round shape doesn't necessarily mean the pearl is more beautiful or valuable. Some pearl lovers actually prefer pear, oval, or baroque shapes over round.


When it comes to pearl grading, color is arguably one of the most complicated standards, since pearls naturally occur in many colors, including yellow, orange, pink, and violet. Diamonds are typically graded on a simple color scale from colorless (most valuable) to yellow (least valuable), but pearl color can have three components: bodycolor, overtone, and orient. Supply and demand in the jewelry industry, affected by things like fashion trends, typically determines the value of a pearl’s color.


Did you know that luster is the most important grading factor for pearls? Luster refers to a pearl's reflection, and it's graded on a scale of Poor to Excellent. "Poor" means that the pearl's reflections are dim and diffused, while "Excellent" means that reflections appear bright and sharp. The differences in luster may be subtle, but they do make affect the pearl's beauty.

Surface Quality

Pearls, just like people, can never be perfect. The same way that we have blemishes, wrinkles, and scars, pearls also have surface imperfections, but some have fewer imperfections than others. If these surface characteristics are minor and limited, then they won't affect a pearl's value greatly. However, many surface issues can actually compromise a pearl's durability.

Nacre Quality

Nacre is a material that makes up the pearl's outer coating. A pearl's nacre quality is closely related to its luster, since a thin nacre will negatively impact the pearl's luster and durability.


Matching is most important for pearl strands, since the overall value of a stand will increase when the pearls within it match as closely as possible in size, color, luster, and shape. Matching natural pearls is more challenging than most people realize!

Not all pearls will be graded by the GIA, and you shouldn't necessarily make your purchase decision based on a positive grading, poor grading, and complete lack of grading. Pearl grading is most important when you're purchasing pearls as an investment or spending an extraordinary amount of money on a piece of pearl jewelry. However, anyone interested in buying any kind of pearl jewelry should at least be aware of the quality factors, so they can consider them in their milestone jewelry purchase. Overall, a pearl is only as valuable as how it looks to you and how it makes you feel.


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