As a significant improvement to its well-known comprehensive pearl classification system, the GIA 7 Pearl Value FactorsTM, the Gemological Institute of America (GIA) is implementing an extended method of assessing nacre on all pearl classification reports.
In the past, GIA categorized nacre as either “acceptable” or “unacceptable” depending on a number of criteria. “Unacceptable” indicated low-quality nacre that could affect durability, such as thinness, chalkiness, or damage, but “acceptable” indicated expected commercial nacre quality in terms of thickness, layering, and condition. The new scale will characterize and categorize the nacre’s continuity and quality in a manner that is more in line with other quality characteristics, as prompted by observations and demands from participants in the international pearl trade.
The nacre scale was created by carefully analyzing a large number of pearl samples with different surface and subsurface characteristics that can reveal variations in nacre layering and continuity during the course of a pearl’s development. Due to this modification, most submitted pearls will now be categorized as having Good nacre instead of Acceptable.
The degree of eye-visible movement (nacre variation) on the surface or sub-surface layers of nacre, as well as the post-harvest condition, including wear, damage, modifications and treatments, and trade standards for thickness, will be used to evaluate the nacre of a pearl, strand, or other item during classification service. All GIA pearl classification reports will specify which of the five GIA classification ranges—Excellent, Very good, Good, Fair, and Poor—the nacre will fall into.
“Nacre development is crucial throughout a pearl’s growth since it determines other value criteria such as size, shape, luster, and surface quality.” Tom Moses, Executive Vice President and Chief Laboratory and Research Officer, stated that nacre thickness and continuity also have an impact on the endurance of pearls. “This modification to the nacre quality scale enhances the existing nacre quality description for the GIA 7 Pearl Value Factors categorization system, better serving our clients.”