Grading Systems

Until today, there is no universal grading and evaluation system, although there have been a number of attempts and efforts.

The original GIA (the Gemological Institute of America) “Pearl Grading System” for Akoya cultured pearls and freshwater cultured pearls has since become the basic of all pearl grading; it includes the quality factors size, shape, luster, nacre thickness and surface.

At the beginning of 2000, the GIA presented a new grading system in the new edition of its “Pearl Course”, for which it received generous financial support from organizations within the cultured pearl industry. The new system considers seven known quality factors and integrated them into a descriptive system:

• Size
• Shape: the factor distinguishes symmetrical shapes and fancy shapes;
• Color: the factor distinguishes body color, overtone and orient. In order to determine body color a “Color Reference Chart” is introduced that considers both hue and saturation. The card can be used for all types of cultured pearls;
• Luster: The factor is divided into four grades which are Excellent, Good, Fair and Poor;
• Surface: the factor is divided into four grades
• Nacre thickness: the factor is divided into four grades as well;
• Matching of pearls within strings or piece of jewelry and it is divided into four grades, too.

This system grades pearls on a scale from HADANAMA to A, with HADANAMA being the highest grade. The grades are as follows:

• HADANAMA: Virtually flawless on the surface with the highest luster;
• AAA: Surface luster is very high, and 95% of surface will be free of inclusion;
• AA: The surface have high luster, and at least 75% of the surface is free of inclusion;
• A: The lowest gem grade pearl, with low luster and more than 25% inclusion on the surface.

For Tahitian cultured pearls and South Sea cultured pearls, the official French Polynesian classification system on a scale from A to D.

• Grade A: Perfect surface or slight growth characteristics, which altogether account for less than 10% of the surface. Luster is good;
• Grade B: The total of growth characteristics accounts for less than 30% of the surface. Luster is medium;
• Grade C: Growth characteristics account for less than 60% of the surface. Luster is medium to low;
• Grade D: Growth characteristics account for more than 60% of the surface. Luster is low to very low or is not present.

The AAA-A Pearl and A-D grading system are the two major pearl grading systems in pearl industry around the world at this moment.

And the thickness of the pearl layer that grow onto the nucleus has the highest influence on both quality and value of pearls,

The tables below show the scales of these two pearl grades:

Freshwater Cultured pearls and Akoya Cultured pearls

Tahitian Cultured pearls and South Sea Cultured Pearls.