Micro-World Gems & Gemology, Spring 2022, Vol. 58, No. 1

An A-maze-ing Fingerprint in Spinel

Web-like fingerprint seen in a Vietnamese 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.

E. Billie Hughes is a gemologist and co-founder of Lotus Gemology in Bangkok.