gems, spinel, Tanzania, inclusions, diopside, phlogopite, edenite

The authors examined a 7.01 ct spinel reportedly from Tanzania. Under short-wave (254 nm) ultraviolet light, a small fluorescent spot was observed on the stone’s surface, caused by cut-through crystal inclusions. Micro-Raman analysis identified the inclusions as diopside, phlogopite, and edenite, forming a cluster of transparent crystals associated with a dark, opaque pyrite grain. In reflected light, the inclusions showed luster distinct from the spinel host, with the pyrite exhibiting a golden metallic luster. Under short-wave ultraviolet light, the crystals fluoresced in different colors: white for diopside, yellow for phlogopite, and blue for edenite. The study demonstrates that fluorescence from mineral inclusions, although often overlooked, can provide useful clues for their identification.