The Gemological Institute of America (GIA) recently examined a pair of earrings it found to contain two assembled pearls with each base showing distinct layers of materials.

The button-shaped, 7.40- and 9.37-carat pearls recently arrived at the GIA’s Mumbai laboratory to undergo investigation to establish accurate identification, according to an article in the fall issue of the institute’s Gems & Gemology quarterly journal.

Upon receiving the earrings, the lab unmounted the pearls. The inner layer exhibited a concentric acicular core, with prominent cracks typical of a natural pearl growth structure. This was encased in a yellowish translucent layer with brown, bubble-like inclusions, probably adhesive used to join the inner core and outer nacreous dome. Meanwhile, the outer layer of the pearls appeared smooth, displaying an overlapping aragonite platelet, while each base showed distinct layers of materials from the assembly process.

Real-time X-ray microradiography (RTX) imaging revealed both pearls had unusual internal structures, with rounded natural-looking cores and button-shaped outer domes lacking growth features. The domes appeared to be blister-related materials, but the facility could not determine whether their origin was natural or cultured. Imaging and surface evidence indicated the components were bonded with a radiolucent adhesive, and both gems had large internal voids typical of assembled or mabe-type pearls.

In addition, X-ray fluorescence led to weak greenish reactions on the faces of the pearls and greenish-yellow on the bases, with inert cores. Energy-dispersive X-ray (EDX) analysis confirmed a saltwater origin.

This pair of earrings features an uncommon type of assembled pearl, where natural cores mimic the appearance of genuine pearl growth. Accurate identification requires thorough laboratory testing, as mounted assembled pearls can easily mislead the naked eye.

Image: The finished pearl jewelry (left); the base and x-ray imaging of the pearls. (Gemological Institute of America)

Courtesy : Rapaport