The Gemological Institute of America (GIA) has launched an expanded approach of evaluating nacre on all of its pearl classification reports on 20 May 2025. It believes will provide an important update to the institute’s pearl classification system which is the GIA Seven Pearl Value Factors.
Previously, the GIA classified nacre as “acceptable” or “unacceptable.” It used “acceptable” to indicate expected commercial nacre quality in terms of thickness, layering and condition, while “unacceptable” described those of poor quality, with features such as thinness, chalkiness or damage, said the GIA.
According to GIA, its 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. The institute will evaluate the pearl’s nacre based on the degree of eye-visible movement found on either the surface or subsurface layers of nacre, in addition to the post-harvest condition, which includes wear, damage, modifications and treatments, as well as trade standards for thickness.
The nacre will fall into one of GIA’s five classification ranges of pearls (excellent, very good, good, fair and poor). It will state these new categories on all of its pearl classification reports.
Tom Moses, executive vice president and chief laboratory and research officer of GIA, said: “Nacre formation plays a critical role during a pearl’s growth, as its structure influences other value factors such as size, shape, lustre, 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 Seven Pearl Value Factors classification system that better serves our clients.” (Photo courtesy: GIA)
28-05-2025
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