GIA introduces expanded Nacre Scale to all pearl classification reports

GIA (Gemological Institute of America) has expanded its approach to evaluating nacre on all pearl classification reports, providing an important update to the institute’s comprehensive pearl classification system, the GIA 7 Pearl Value Factors.

The nacre will now fall into one of GIA’s five classification ranges (Excellent, Very good, Good, Fair, and Poor), which will be stated on all GIA pearl classification reports.

Previously, GIA classified nacre as “Acceptable” or “Unacceptable” based on several factors. 

Acceptable denoted expected commercial nacre quality, in terms of thickness, layering and condition, while “Unacceptable” denoted poor quality nacre that may impact durability, such as thinness, chalkiness or damage. 

Prompted by observations and requests from members of the global pearl trade, the new scale will describe and classify the continuity and quality of the nacre in a way that is “more aligned” with other quality factors.

The nacre scale was developed through detailed examination of a wide assortment of pearl samples with varied surface and sub-surface features that can indicate differences in nacre layering and continuity during a pearl’s growth. 

As a result of this update, the majority of pearls submitted will now be classified as having Good, rather than Acceptable, nacre.

During classification service, the nacre of a pearl, strand or other item will be evaluated based on the degree of eye-visible movement (nacre variation) found on either the surface or sub-surface layers of nacre, in addition to the post-harvest condition including wear, damage, modifications and treatments, and trade standards for thickness. 

Tom Moses, executive vice president and chief laboratory and research officer at GIA, said: “Nacre formation plays a critical role during a pearl’s growth, as its structure influences other value factors such as size, shape, luster, and surface quality. Nacre thickness and continuity also affect the pearl’s durability. 

“This update on the nacre quality scale provides improvement to the existing nacre quality description for the GIA 7 Pearl Value Factors classification system that better serves our clients.”