Fashioned Queen Conch Shell Bead
Conch pearls are prized for their porcelaneous surface and distinctive flame-like pattern, characterized by a regular arrangement of parallel elongated crystals that create a silky sheen (H.A. Hänni, “Explaining the flame structure in non-nacreous pearls,” SSEF, 2009). Highly valued Queen conch pearls, produced by the Aliger gigas species (formerly Strombus gigas or Lobatus gigas), are known for their exquisite pink coloration, flame structure, and porcelaneous luster. Queen conch shells are widely used for crafting and jewelry accessories and sometimes used to simulate the appearance of natural pearls.
Recently, GIA’s Mumbai laboratory received a drilled light pink bead for pearl identification, measuring 10.20 mm in diameter and weighing 7.50 ct (figure 1). Most Queen conch pearls are oval, semi-baroque, or baroque, and it is very rare to find a perfectly round conch pearl similar to the submitted specimen. In addition, an obvious banded structure was observed on the surface, which raised suspicions of a fashioned shell (E. Fritsch and E.B. Misiorowski, “The history and gemology of Queen conch ‘pearls’,” Winter 1987 G&G, pp. 208–221). The banded structure was arranged in a distinct concentric ring pattern resembling a bull’s-eye (figure 2A), with alternating white, cream, and light pink bands covering half of its surface. The parallel band lines appeared to run throughout the bead when observed using transmitted fiber-optic illumination (figure 2B), consistent with the parallel striations revealed by real-time X-ray microradiography imaging (figure 2C). Under high magnification, prominent flame structures with long, slender linear striations were visible (figure 2D).
Ultraviolet/visible/near-infrared reflectance spectra showed absorption features at 280 and 368 nm and a broad band centered at 512 nm, similar to those seen in natural orangy pink conch pearls, confirming their natural color origin (figure 3). Raman analysis using 514 nm laser excitation revealed a doublet at 702/704 cm–1 and a peak at 1086 cm–1, indicative of aragonite. Significant polyenic pigment peaks were previously observed at 1125 and 1514 cm–1, indicative of natural color (S. Karampelas et al., “Raman spectroscopy of natural and cultured pearls and pearl producing mollusc shells,” Journal of Raman Spectroscopy, Vol. 59, No. 1, 2019, pp. 1813–1821). After thorough analysis, the specimen was confidently determined to be a fashioned shell bead imitation originating from the shell of an Aliger gigas gastropod (Queen conch).
Shell imitations of pearl hold a long-standing history as fashionable jewelry pieces targeting a wide consumer base. These imitations are occasionally misrepresented as “shell pearls” or simply “pearls,” potentially misleading less experienced buyers (Summer 2014 Lab Notes, pp. 153–154). Their close resemblance to natural and cultured pearls often leads consumers to seek laboratory testing. The fashioned shell specimen under examination was relatively straightforward given the distinctive banded structure, a feature normally absent in pearls. However, it is crucial to observe subtle traits and compositions that can distinguish genuine pearls from imitations. Shell is the most popular material used for porcelaneous pearl imitations, and sometimes it is sourced from the same mollusk species as the pearl being imitated, causing similar color and surface appearance. Therefore, caution and scrutiny are always essential when purchasing pearl products.
