| In this study,the mineralogical,chemical and spectral characteristics of gem-quality rhodochrosites from Guangxi,China and Katamaka,Argentina were investigated by the macro-methods and micro-methods on the basis of relevant literatures.The properties difference between China and Argentina of rhodochrosites were also studied by means of X-ray fluorescence spectrometer?XRF?,electron probe micro-analyzer?EPMA?,inductive coupled plasma emission spectrometer?ICP?,X-ray powder diffractometer?XRD?,ultraviolet-visible?UV-Vis?,fourier transform infrared spectrum?FT-IR?,and raman spectrometer?Raman?.The results showed that the physical properties of all the samples of gem-quality rhodochrosites were remarkably similar.The rhodochrosites were pink with few white bands,transparent to opaque,weak to non-fluorescence to either long-or short-wave UV.The refractive indices,Moh's hardness and relative density of samples were 1.60,35,3.453.60 g?cm-3,respectively.It was found that the growth structure,crystal inclusion,two-phase gas-liquid inclusions in the magnified observation images using polarizing microscope of samples.The gem-quality rhodochrosite from China were mostly made of medium-fine grains with better self-shape.The obvious ring structure was not observed and the contact surface of red and white parts was straight.The argentina gem-quality rhodochrosite had obvious ring band structure,and the contact surface of red and white parts was lacery and serrated.The main mineral composition of gem-quality rhodochrosite was MnCO3,which contained a little of impurity elements such as Ca,Fe and Mg.The contents and species of trace elements in rhodochrosite from China and Argentina were quite different.The contents of Mn,and Ca,Mg,Fe in rhodochrosite were,China,98%,0.150.19%;Argentina,9497%.The rhodochrosite from China contains Ni and lacks Co.The rare earth distribution was divided into right-leaning mode of light rare earth relative depletion and heavy rare earth relative enrichment.The results also showed that the rhodochrosite may be generated by hydrothermal origin and weak alkaline formation environment due to its obvious Ce depletion.The Spectroscopic analysis showed that the rhodochrosite was a self-color mineral.Its red was produced by d-d transition of Mn2+.The UV-Vis absorption peaks of the rhodochrosite from China and Argentina were concentrated at 310 nm,342 nm,362 nm,407 nm,446 nm and 550 nm.The higher the content of manganese,the stronger the absorbance,the thicker the red.Some Rhodochrosite appeared white under the comprehensive influence of composition,structure and porosity.The contents of Mn,and Ca,Mg,Fe in the white part of rhodochrosite from China and Argentina are between 1314%.The rhodochrosite belongs to trigonal system with the typical calcite-type structure,which infrared and Raman spectra was caused by the internal and external vibration of[CO3]2-.The FT-IR absorption peaks of samples mainly contained 1420(±cm-1),870(±cm-1)and 720(±cm-1),belonging to the absorption peaks of[CO3]2-.The series weaker Sum-frequency peaks and frequency-doubled peaks were observed at 1804(±cm-1),2363(±cm-1),2486(±cm-1),2584(±cm-1)and 2837(±cm-1),2974(±cm-1).The absorption peaks of Raman activity included vos(179 cm-1183 cm-1),vob(286 cm-1297 cm-1),vib(717 cm-1),vs(1083 cm-1),vas(1411 cm-11413 cm-1)and vib+s(1725 cm-11727 cm-1). |
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