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Spinel is a precious gem with a long history, but people are far less familiar with it. Previous studies on Mogok spinel from Myanmar focused on inclusion analysis, chromogenic mechanism with a single-color gemstone and heat treatment, whereas systematic studies on varicolored gem-grade spinel are lacking. In this study, the gemological and geochemical analysis of four colors of spinel samples from Mogok were carried out for basic gemology, inclusion morphology and identification, spectroscopy and geochemistry. The aim was to explore the occupation of elements of spinels in the crystal structure, as well as the chromogenic mechanism of varicolored spinels and the geological and geodynamic conditions of the formation. Mogok spinel samples are characterized by octahedral negative crystals filled with calcite and chondrodite inclusions, indicating that they are derived from a marble metamorphic-type deposit. The spinel samples of four colors are magnesia–alumina spinel (MgAl2O4). The contents of V and Cr in Mogok spinel are generally high, with a significant high content of Zn being the most characteristic, and trace elements vary greatly. The infrared spectra of spinel samples in different colors are basically similar. According to the UV–Vis spectrum, pink and red samples are mainly colored by Cr and/or V, whereas orange samples are mainly colored by V. Two wide absorption bands in the range 300~600 nm are mainly attributed to the spin-allowed transition and spin-forbidden transition of Cr3+ and/or V3+. The purple samples are mainly colored by Fe and the UV–Vis spectrum is mainly attributed to the spin-forbidden transition of TFe2+. This study is a favorable supplement to the research on Mogok spinels of various colors from multiple perspectives.

With mineral in situ testing technology and ore deposit geochemistry development, calcite has become a hot topic in studying carbonate minerals. Four large-grain calcite crystals from Fujian, China, were used for a detailed study. This study provides a comprehensive data set through mineralogical standard properties and spectral characteristics, including Fourier transform infrared, X-ray fluorescence spectrum, and Raman spectroscopy. Major elements were analyzed using X-ray fluorescence (XRF) and Micro-XRF. A high-resolution gas-source stable isotope ratio mass spectrometer was used to test C-O isotope characteristics. The four samples’ spectral characteristics and phase composition show excellent uniformity, all with the same characteristic peaks, indicating that they are pure calcite without other impurity minerals. C-O isotope characteristics indicate that Fujian calcite has mantle genetic characteristics, which may be affected by marine carbonate dissolution or sedimentary rock contamination. The variation of Fe and Mn contents may indicate that the four samples formed at different metallogenic stages.