宝石级氟磷锰矿的化学成分及光谱学表征

氟磷锰矿是一种稀有矿物,宝石级氟磷锰矿可呈现高饱和度的红橙色.选取三颗来自巴基斯坦的样品,通过电子探针、拉曼光谱、红外光谱和紫外-可见光吸收光谱进行系统研究,旨在获得其化学成分、光谱学特征,分析致色离子,为其品种鉴定、优化处理等提供重要数据.样品平均化学成分化学式为(M n1.66,Fe0.17,Ca0.15,Mg0....

Chemical Constituents and Spectra Characterization of Gem-Grade Triplite

Triplite is a rare mineral，and gem-grade triplite can present a highly saturated reddish orange. In this paper，three samples from Pakistan are selected for systematic research through Electron Microprobe，Raman spectra，Infrared spectra and UV-Vis absorption spectra. The purpose is to obtain their chemical composition and spectral characteristic，analyze the chromogenic ions，and provide important data for their species identification and optimization processing. The chemical formula of average chemical composition is (Mn_1.66, Fe_0.17, Ca_0.15, Mg_0.03)_Σ2.02P_0.99O_4.14(F)_0.82，which belongs to the Mg-rich and Fe-poor triplite. And it has a similar chemical composition with the gem-grade triplite produced in the Shigar Valley of Pakistan in the literature. Raman spectra and Infrared spectra show that the main vibration group of triplite is PO3-₄ group. The main peak of Raman spectra is located at 980 cm-1，which can be used to analyze the substitution relationship between OH- and F. The intensity contrast of the 450 and 427 cm-1 bimodal peaks can reflect the substitution relationship between Mn2+ and Fe2+. The Infrared spectra has absorption peaks in the 400～650 and 900～1 200 cm-1 band，which can reflect the substitution relationship between OH- and F, Mn2+ and Fe2+. Thus，Raman spectra and Infrared spectra can be used to clearly distinguish the isomorphic minerals：triplite，wolfeite and zwieselite. In the UV-Vis absorption spectra，the strong absorption peak centered at 406 nm is caused by the spin-forbidden transition of Mn2+. The weak absorption peak centered at 455 nm is caused by the spin-forbidden transition of Fe2+，and Mn2+ also has a certain effect on this peak. The absorption peak centered at 533 nm is caused by the transition of Mn2+，6A_1g(S)→4T_1g(G). So the samples show a reddish orange color，which is an idiochromatic mineral. There are common isomorphisms in the triplite group minerals. Raman spectra and Infrared spectra can identify triplite accurately，and EMPA can provide important information for the traceability of its origin.