Oil treatment has a significant impact on the appearance of an apatite.
Fissure filling of gemstones is an age-old treatment that can improve a stone’s clarity (Gems & Gemology, Fall 2020 Gem News International, pp. 443–444). By introducing oil or other fillers such as resin into the stone, the treater can minimize the appearance of fissures.
Recently we had the opportunity to observe this treatment up close in an apatite cabochon brought to our laboratory for photography while it was still untreated. Then the sample was oiled by Jeffery Bergman and returned to the laboratory for observation and photography.
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| Figure 1. Left: On the base of this apatite cabochon (15 × 15 × 13 mm), a large, reflective fissure can be observed with fiber-optic illumination. Right: After the oil filling, the same fissure is much less noticeable and the iridescent reflective area is considerably smaller, enhancing the sample’s clarity. Photos by E. Billie Hughes. | |
Upon examination before and after, the effects of the treatment were clear. On the base of the cabochon, a large, reflective fissure became less visible after oiling (Figure 1). Using fiber-optic illumination, it was apparent that the filler had diminished the reflective appearance of the fissure, with only small highly reflective areas remaining (Figure 2). Darkfield illumination also revealed a stark difference in appearance: The filler had rendered large dark areas filled with air nearly invisible (Figure 3).
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| Figure 2. A close-up of the fissure before and after oil treatment, shown in diffuse fiber-optic illumination. Left: Before oiling, the fissure is easily visible and highly reflective. Right: After oiling, the reflection is more muted and less noticeable, with only a small highly reflective area remaining. Photomicrographs by E. Billie Hughes; field of view 10 mm. | |
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| Figure 3. Left: Before filling, transmitted light shows dark areas where air has become trapped in the fissure, making it more visible. Right: Treatment with oil minimizes the dark areas, enhancing clarity. Photomicrographs by E. Billie Hughes; field of view 27 mm. | |
This microscopic observation serves as a reminder of the significant impact clarity enhancement can have on gems of all types.
About the Author
E. Billie Hughes is Co-Founder and Managing Director of Lotus Gemology. She oversees the company's day-to-day operations while continuing gemological research and laboratory work. After graduating from UCLA in 2011, Billie became a Fellow of the Gemmological Association of Great Britain (FGA) in 2013. Her research focuses on ruby and sapphire, including low-temperature heat treatment, and she has authored and co-authored articles in leading gemological journals. An accomplished field gemologist, she has traveled to gem deposits around the world, including nearly every major ruby and sapphire locality.
Billie is an internationally recognized educator who has lectured for trade organizations, museums, and luxury jewelry houses. She has collaborated extensively with Van Cleef & Arpels on educational programs and lectures. An award-winning photographer and photomicrographer, her images have received honors in the Nikon Small World and Gem-A competitions and have appeared in publications including National Geographic and Forbes. She is also the creator of Hyperion, Lotus Gemology's online inclusion database, reflecting her commitment to making gemological knowledge more accessible.
Billie developed an interest in gemstones from an early age, accompanying her parents on expeditions to mines and gem-producing regions around the world. That lifelong passion for fieldwork, laboratory research, education, and photography continues to shape her work at Lotus Gemology today.
Notes
This article first appeared in Gems & Gemology, Spring 2022, Vol. 58, No.1, pp. 62–63.