Locality identification of high‐quality inky black omphacite jades (inky jades) from Myanmar and Guatemala is becoming increasingly urgent. In this study, Raman, Fourier transform infrared (FTIR), and energy‐dispersive X‐ray fluorescence spectroscopy (EDXRF) were performed to distinguish samples of inky jade from the two localities. The Raman spectra revealed the presence of several types of minor minerals in Guatemalan samples, including titanite, albite, orthoclase, taramite, celsian, and cymrite, whereas the Myanmar samples consisted almost entirely of omphacite. Taramite and lath‐like celsian occurred only in Guatemalan samples and had significance in locality tracing. The Raman and FTIR reflectance spectra of omphacite shifted to low wavenumbers in proportional to isomorphic substitution Na+Al3+ → Ca2+(Mg2+, Fe2+). Semiquantitative calculations based on the Raman (~680 cm−1) and IR modes (~658, ~576, and ~424 cm−1) showed consistent jadeite end‐member components (~43% to ~64%) in the Myanmar samples, whereas those (~23% to ~87.5%) of the Guatemalan samples were wider and generally lower. In addition, the full width at half maximum values (FWHMs) of Raman shifts near 680 cm−1 in the Myanmar samples (avg. 15.03 cm−1) were less than those (avg. 16.81 cm−1) of the Guatemalan specimens. Linear discriminant analysis (LDA) based on Raman spectroscopy identified most samples with accuracy of 85.5%. Combined with results by EDXRF, these analyses revealed the characteristics of a relatively narrow range of Na+Al3+ → Ca2+Mg2+ isomorphism for the Myanmar jades and a more developed Na+Al3+ → Ca2+(Mg2+, Fe2+) isomorphism for the Guatemalan jades. This study might have implications for commercial applications, archeological research, and judicial expertise.
Unique finer-grained interstitial textures, occurring as small blocks or irregular shapes of 0.15–10 mm, were found merging in the coarse-grained textures of Kazakhstan jadeitite. According to the mineral content, the interstitial texture could be classified into two types: Type I, consisting of almost all jadeite crystals, minor omphacite, and little analcime, and Type II, comprising mainly omphacite and analcime, with minor jadeite crystals. They both showed no obvious preferred orientation and have distinct boundaries with the coarse-grained textures but appear more transparent, with finer grain sizes and higher degrees of idiomorphism. The coarse-grained textures include granitoid textures and radial clusters. The granitoid textures formed by euhedral to subhedral prismatic grains usually show rhythmic zoning patterns and parallel intergrowths. Furthermore, fluid inclusions contain H2O and CH4, and it was supposed that the coarse-grained textures were formed by the precipitation of jadeitic fluids. However, perhaps due to the insufficient supply of the fluids or sufficient space, some interspaces were left among the coarser-grained jadeitite. Afterward, these interspaces were filled with precipitation of the successor H2O-richer fluids under a different P–T condition from that of the former coarser-grained jadeitite, and consequently, two kinds of interstitial textures formed. Such interstitial textures seem to appear only in Kazakhstan and therefore could serve as a typical visual identification feature of Kazakhstan jadeitite.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.