Glass Imitation of Cat’s-Eye Chrysoberyl
The Hong Kong laboratory recently examined a ring mounted with an estimated 5.56 ct brownish yellow cat’s-eye cabochon (figure 1). The client submitted the stone as cat’s-eye chrysoberyl, which it resembled at first glance. Standard gemological testing yielded a spot refractive index of 1.57, well below chrysoberyl’s range of 1.74–1.75. Under short-wave UV radiation, the stone displayed strong chalky fluorescence. Microscopic observation revealed long parallel tubes creating a cat’s-eye when viewed from the top and a honeycomb structure when viewed from the side of the stone (figure 2). This confirmed the material was fiber-optic glass, made by fusing together very thinly spun glass fibers. Infrared spectroscopy showed two broad absorptions centered at 3500 and 2670 cm–1 associated with artificial glass, further validating our identification.
Artificial glass has been used as an imitation for different gems such as star sapphire (Fall 2021 Lab Notes, pp. 261–262), Paraíba tourmaline (Winter 2020 Lab Notes, pp. 518–520), nephrite and jadeite (Spring 2019 Lab Notes, pp. 93–94), and blue amber (Fall 2019 Gem News International, pp. 443–444). Its color and appearance can often lead to misidentification. Therefore, conducting basic gemological tests and observing the stone under a microscope is important, especially when the stone is set in jewelry.
