Xueying Sun

This article reports on the recent mining and production status of ruby in Longido, Tanzania. Faceted-grade rubies and their matrix from Longido Area, Tanzania, were investigated by standard gemological testing, including FTIR, UV-VIS, Raman spectra, and LA-ICP-MS. Microscopic observations revealed dense needle-like and triangular inclusions, distinct growth lines, and color banding as typical inclusions. In agreement with the Raman results, the transmission FTIR spectrum confirmed the presence of aluminum hydroxide. The Raman spectra identified associated minerals and inclusions, including zoisite, parasites, feldspar within the matrix, rutile, and diaspore in the ruby host. The chemistry analysis revealed a high amount of Cr and relatively low iron as a good indicator of geographic origin.

Purple-violet gem spinels from Tanzania and Myanmar have been investigated for their gemological, spectroscopic, chemical, and colorimetric characteristics. Samples TS and MS both had a purple hue with a pinkish or brownish secondary tone and medium–strong saturation. We identified a number of inclusions, including dolomite, phlogopite, and forsterite in Tanzanian spinel and magnesite, apatite, baddeleyite, anhydrite, pyroxene, and graphite in Myanmar spinel. Tanzanian spinels have slightly lower FWHM (full width at half maximum) values of the 406 cm⁻¹ line in the Raman spectrum and the Cr³⁺ zero phonon line in the PL spectrum compared to samples from Myanmar. Fe, Mn, Cr, V, and Zn are proved as useful discriminators to distinguish these two geographic locations. UV-Vis-NIR spectra and CIE L*a*b* parameters are compared with trace element chemistry. Both samples are colored by Fe²⁺, with minor Fe³⁺, Cr³⁺, and V³⁺. Cr, V, and Fe are combined to influence the hue angle and lightless of purple spinels from Tanzania. However, due to the relatively stable content in Myanmar samples, Fe shows a minor effect on these two parameters. It is worth noting that all inclusion scene, spectral, and chemical characteristics, as well as the comparison presented in this study are of a limited number of samples from Tanzania and Myanmar.

In the present study, we collected and investigated spinels from the Man Sin deposit in Myanmar using standard gemological testing, microscopic observation, EDXRF, and Raman spectrometry. The color observation was performed under various lighting conditions to show color differences. A very high Cr/Fe ratio is linked with exceptionally strong red fluorescence. Microscopic observation and Raman spectroscopy identified mineral inclusions of colorless phlogopite, molybdenite, hauerite, native sulfur, and calcite. Man Sin spinels are typical Fe– and Zn–poor spinels. Binary and ternary diagrams were used to discriminate each deposit (i.e., Man Sin, Mogok, and Namya in Myanmar) with high reliability. Jedi spinel fever in the Asian market, due to their unique neon color appearance and exceptionally strong fluorescence, is also discussed.

Gemstones usually contain inclusions as the natural hallmark of their formation. Studies on inclusions may contribute to our understanding of the gem and better adapt to the gems and jewelry industry. In this study, we applied advanced 3D Raman mapping and high-resolution X-ray computed tomography (HRXCT) and conducted a thorough experiment on one emerald with a special trapiche pattern containing a colorless core, solid minerals, and fluids. Hematite and magnetite were identified as metallic minerals by the Raman spectrum. The hexagonal core is beryl, and the voids are primarily filled with CO₂ and N₂. HRXCT demonstrated a visualized distribution of these inclusions within the gem host by reconstructing a 3D illustration. Further calculation of the volume of inclusions regarding the host showed that the minerals take up 0.07%, void 0.03%, and the hexagonal core 8.25%. The combined application of Raman-Mapping and X-ray Micro Computed Tomography proved to be a very promising technique for tracing the gemstones by characterizing the unique inclusions (identification and morphology) within the gem host.