A web-like fingerprint creates a maze-like pattern in spinel.
A web-like fingerprint creates a maze-like pattern in this spinel from Vietnam, observed with darkfield and diffuse fiber-optic illumination. Photomicrograph by E. Billie Hughes; field of view 5 mm. Courtesy of Vitalit Gems.
Of the variety of inclusions that can be seen in spinel, perhaps the most familiar are angular octahedral crystals. In many cases, we even see these crystals arranged in neat rows, forming delicate “fingerprint” inclusions.
However, spinel fingerprints can also take on other appearances, as observed in a Vietnamese sample that recently passed through our laboratory (see above). This stone contained a partially healed fissure with a maze-like pattern that was evident when lit with darkfield illumination. With the addition of diffuse fiber-optic illumination, small angular areas of the channels seemed to light up with a highly reflective appearance. Myriad inclusion scenes make spinel a fascinating gem to observe.
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, p. 68.