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Grading Pearls

Pearl Grading Defined

Pearl Grading is the practice of assigning degrees of quality to a pearl or a piece of pearl jewelry based of the quality attributes designated by industry best practices and authority groups such as PSLJ (Pearl Science Laboratory of Japan), SSEF (Swiss Gemological Institute), GIA (Gemological Institute of America) and EGL USA.

There Is No Industry-Wide Standard Pearl Grading System

The single most important thing to understand about pearl grading is that no industry-recognized standards exist. This means every grading system used by every company and pearl producer is unique and subjective. It is therefore impossible to compare grades and grading systems from one vendor or producer to another.



There are Two Major Pearl Grading Scales, but Buyer Beware

Two major grading scales have widespread use are the "AAA-A" scale and the "A-D" scale. These are the most accepted scales and considered standard by nearly all reputable pearl dealers, both retail and wholesale.

Even these scales can become misleading, however, as there is no agreed set of standards. In other words, grading is subjective, and one grade will vary from another when comparing different producers or vendors.

Ask to See the Pearl Grading Descriptions in Writing

For reasons such as these, it's extremely important when purchasing pearls, to be absolutely certain of the meaning of any descriptive terms used by the seller. If possible, ask to see a written description of each grading term, so that you know exactly what the grade implies. Reputable jewelers will be happy to comply with such a request. Only in this way will you be able to determine if the price the seller is asking is reasonable.

The AAA-A Scale

This system grades pearls on a scale from AAA to A, with AAA being the highest grade. This grading scale is common to freshwater and akoya pearls only, but is accepted by many with South Sea and Tahitian pearls as well.

Hanadama Grade Akoya Pearls

There is one grade assigned by a third-party laboratory in Japan to akoya pearls, which does give somewhat of a benchmark for akoya pearl quality as it is supposed to signify the finest of any given pearl harvest, which is separated and sold separately as a fine grade of akoya pearl.

This grade does not mean, however, that the pearls offered with the certificate are truly the finest grade available. Even hanadama grade has a range of quality and without set international standards, this certification can be subjective. To make matters worse, akoya pearls are routinely sold with a certificate that doesn't match the strands or pairs. In other words, there is no guarantee the pearls accompanying the certificate are the graded pearls. Unlike diamond grading, which is exact, weights and exact measurements of each individual pearl are not included with the certificate.

Intermediate Grades And Pearl Grading For Strands

Some reputable sellers may also use intermediate grades for the pearls - those pearls that do not fall in a category but are between two - such as A+ and AA+. Obviously, these grading categories are quite broad and leave room for interpretation and individual judgment. Also note that in multi-pearl pieces such as strands, necklaces, bracelets, etc., every one of the individual pearls may not absolutely meet the indicated grade level. For example, a strand referred to as "AAA" must have most of its pearls as AAA pearls. However, a few pearls could have slightly lower luster or a tiny bit more surface defects. This is because matching is also a primary consideration in multi-pearl jewelry, sometimes even overriding a strict grading of each individual pearl.

The A-D Scale (or Tahitian Scale)

It is important to note that the following grading system can be interchanged with the AAA-A system.

This system grades pearls on a scale from A to D, with A being the highest grade. This is the system used in French Polynesia (based on a government standard there) to grade Tahitian pearls, and South Sea pearls only. It is therefore sometimes referred to as the "Tahitian system." While this system is standard in producing countries, other markets will still utilize AAA-A.
  • A: The highest-quality pearl, with very high luster and only minor imperfections over less than 10% of its surface.
  • B: High or medium luster. Surface may have some visible imperfections, but over no more than 30% of its area.
  • C: Medium luster with surface defects over not more than 60% of the surface area.
  • D: May have many slight defects, but no deep ones, spread over 60% of its surface; or deep defects over no more than 60% of its surface; or a combination of minor and deep defects over no more than 60% of its surface. In this grade of pearl, the luster is irrelevant. Even the most lustrous pearls will be graded D if their surface is blemished to this extent. Pearls below D grade are considered not acceptable for use in jewelry.
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Nacre Is The Final Factor In Grading Pearls

Both of the grading systems described above focus primarily on the luster and surface quality of the pearl to determine its grade. But keep in mind that other factors also contribute to the quality and final grade of any pearl.
One of the most important is the thickness of the nacre, which often determines how durable the pearl will be over time. The thicker the nacre, the stronger and longer-lasting the pearl (provided it is treated well, of course!) For Tahitian pearls, the government of French Polynesia has set a minimum nacre thickness of 0.8 millimeters.
A Pearl with nacre of less than this thickness is not allowed to be sold. Keeping in mind that Tahitian pearls tend to be larger than many other pearls (such as akoyas), you can use this rule as a guideline when evaluating your own potential pearl purchases.

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