Feature Gems & Gemology, Summer 2007, Volume 43, No. 2

Durability Testing of Filled Emeralds

Researchers treated 128 emeralds with nine emerald fillers—Araldite 6010, cedarwood oil, paraffin oil, unhardened and surface-hardened Opticon, a mixture of cedarwood oil and Canada balsam, surface-hardened Norland Optical Adhesive 65, and the solid fillers Gematrat and Permasafe—and then exposed them (along with 14 unfilled emeralds) to common conditions of wear and cleaning. All emeralds were held for about six years, and most were then subjected to one of the following durability tests: exposure to long-wave UV radiation (a component of sunlight), to mild heat and incandescent light in a display case, to five chill-thaw cycles, and to a desiccation environment; ultrasonic cleaning with either warm water or BCR; and cleaning with steam or mild chemical solvents. Changes were evident in about 35% of the filled emeralds after the mild exposure tests (i.e., time, UV radiation, display case); those with liquid fillers were especially susceptible. The desiccation environment made fissures visible in a majority of emeralds. Hard fillers damaged their host emeralds by expanding cracks during durability testing, while chill-thaw cycling extended cracks in both filled and unfilled emeralds. Emeralds with liquid fillers were most susceptible to appearance changes due to ultrasonic cleaning and exposure to ethanol or acetone. Some observations on the effectiveness of different fillers on emerald appearance are also provided.