How Do You Identify Pearls and Their Treatments?

A pearl’s identity decides how it may be described and much of what it is worth. This section covers the tests used, from the simple to the ones only a laboratory can run.

Pearl or imitation#

An imitation pearl is a manufactured product that only looks like a pearl or a cultured pearl.¹ One widely sold kind, made on the Spanish island of Majorca, is a glass bead coated in layers of “pearl essence” made from fish scales.²

GIA researchers who studied those imitations found four tests conclusive for separating them from cultured pearls: refractive index, magnification, X-radiography and the tooth test.² In the tooth test, the cultured pearls they tested felt gritty and the imitations smooth.²

In the United States, an imitation must be called “imitation”, “artificial” or “simulated” whenever the word “pearl” is used. Names such as “faux pearl” and “fashion pearl” need the same qualifier.¹ The page how to tell if pearls are real explains each check, and real vs imitation pearls what imitations are made of.

Natural or cultured#

Telling a natural pearl from a cultured pearl takes a laboratory. X-ray radiography and X-ray computed microtomography are central to the work,³ because a natural pearl shows no bead or curved cavity at its center and a uniform, onion-like structure.⁴ The natural pearls section explains why this matters.

Saltwater or freshwater#

The water a pearl grew in shows in its chemistry. Freshwater pearls contain more manganese and barium, and less strontium, than saltwater pearls.⁵ A GIA report states whether pearls grew in freshwater or saltwater, and which mollusk produced them when that can be determined.⁶

Treatments#

Pearls might be dyed, impregnated or coated, and some are bleached or irradiated. GIA notes that bleaching and irradiation can be stable during normal wear.⁷ Examples include irradiated gray or blue Akoya, whose shell bead darkens inside,⁸ and dyed “golden” cultured pearls, some of which show little sign of the dye on the surface.⁹

Treatments must be disclosed. CIBJO’s standards require a treatment such as bleaching, dyeing, coating, heating or irradiation to be named next to the words “cultured pearl” and explained to the buyer before the sale closes.¹⁰ French Polynesia’s pearl law requires treated pearls to be labeled as treated.¹¹ The page dyed and treated pearls covers each treatment and how labs find it.

What a laboratory tests#

GIA has identified and classified natural and cultured pearls since 1949.¹² Its gemologists identify the pearl type, the mollusk and any detectable treatments with standard gem testing and with real-time X-radiography, UV-Vis reflectance spectroscopy and X-ray fluorescence, and use computed microtomography when a loose pearl needs more detailed analysis.¹² SSEF’s reports likewise separate natural from cultured pearls, beaded from beadless, and saltwater from freshwater, and indicate treatments.¹³