湖南郴州铅磷灰石矿物光谱学特征

The Mineralogical and Spectroscopic Characteristics of Phosphohedyphane From Chenzhou of Hunan Province

近期,在湖南郴州市东南15km柿竹园铅锌矿区黏土层中发现宝石级铅磷灰石标本。因该矿物罕见,且与多种磷酸盐矿物的谱学特征类似,难以鉴别。本文采用常规测试方法结合红外光谱、拉曼光谱、能量色散X射线荧光光谱(EDXRF)和X射线粉末晶体衍射(XRD)分析技术,对该地区的4块铅磷灰石样品的微观结构、元素组成和光谱特征进行了综合测试和对比分析,并将其与鉴定特征类似的磷酸盐矿物进行了简单比较,以探讨该矿物的光谱鉴别特征。常规测试显示,该矿物为半透明黄绿~绿色六方柱微晶簇;晶面呈玻璃~油脂光泽;粒径0.1~0.8 mm,高0.1~1 mm;相对密度为4.487~5.331g·cm^(3);白色条痕;Mohs(莫氏)硬度为4。样品的红外指纹光谱主要由磷氧四面体分别位于~1090~1010和~589~546cm的伸缩和弯曲振动组成,与氟-铅磷灰石的特征指纹光谱一致。除PO_(4)^(3-)特征谱带外,部分样品在804~797和843~852cm出现AsO_(4)^(3-)和CO_(3)^(2-)振动弱带,可能是结构中的部分PO_(4)^(3-)被替代所致。拉曼光谱分析显示,样品具有铅磷灰石特有的磷酸根基团位于976/936cm的拉曼位移,402/426/558/586cm系列PO_(4)^(3-)弯曲振动和170~214cm晶格振动带。此外,820~826cm谱带为(AsO_(4))^(3-)特征振动。EDXRF半定性分析显示,样品主要由Ca,Pb,P,和Cl等元素组成,与铅磷灰石(Ca_(2)Pb_(3)(PO_(4))_(3)Cl)的主要组成元素一致。XRD主要谱线的2θ角、d值和相对强度分别为10.603/22.351/28.261/31.047°,8.3365/3.9744/3.1553/2.8782°,59.1/36.4/30.0/100,分别对应100/110/210/211面网,与氟-铅磷灰石的衍射d值基本一致。综合样品的相对密度值、振动光谱和XRD数据等分析结果可知,实验样品属于铅磷灰石系列矿物中的氟-铅磷灰石。该工作对国内首次发现的氟-铅磷灰石的多种光谱特征进行了分析,为认识、准确鉴别该类矿物和进一步研究提供参考。

Recently a rare mineral of the Phosphohedyphane series was discovered in Hunan Province of China.It occurs in the clay adits above the Pb-Zn deposit,the Shizhuyuan,about 15km east-south of Chenzhou.Determination of the mineral is difficult because its mineralogical and spectroscopic characteristics are similar to some phosphate minerals.Routine determinative procedures and spectroscopy analysis were carried out to investigate the mineral morphology,microstructure,spectroscopy features and partial chemical compositions of 4samples.The crystals occur as subtransparent,yellow-green to bluish-green,the aggregate of micro-crystals.Crystal faces exhibit vitreous to greasy luster.The mineral has a Mohs hardness of approximately4.The relative gravity is 4.487~5.331g·cm^(3).The observation by stereoscopic microscope shows that crystals are hexagonal prisms,as individuals up to about 1 mm in length and≤0.8 mm in diameter.Crystals occur in subparallel intergrowths and irregular clusters.The specimens’infrared spectra show good agreement with Fluorphosphohedyphane.The vibration mode and frequency of PO_(4)^(3-)determine the infrared spectrum’s main feature of samples.The phosphate ions’asymmetry stretching vibrations appear at about 1090/1010cmand their symmetry stretching vibrations appear at 934cm.Correspondingly,their bending vibrations appear at about 589/566/546cmwith weak spilt bands of CO_(3)^(2-)and AsO_(4)^(3-)from the infrared absorption spectroscopy.The Raman spectra analysis proves the phosphate ions stretching vibrations appear at about~400/426cmwhile the bending vibrations appear at~558/586cmwith symmetric stretch at~936/976cmand asymmetry vibration at about 1060cm.Two Raman bands at~170~214cmare assigned to lattice vibration.In addition,there is a notable band of AsO_(4)^(3-)at~822cmin the Raman spectra.The results of semi-qualitative chemical composition analysis by Energy Dispersive X-ray Fluorescence(EDXRF)show the main elements of Pb,Ca,PO_(4)^(3-)and Cl,with trace elements of Cu,Fe,Zn,et al.The 2θ°,d-spacing,hkl and intensity of main Powder X-Ray Diffraction(XRD)lines are 10.603/22.351/28.261/31.047°,8.3365/3.9744/3.1553/2.8782?,(100/111/210/211),59.1/36.4/30.0/100respectively.The samples’d-spacing is smaller in comparison with Phosphohedyphane and closely matches Fluorphosphohedyphane’s.The integraded analysises of relative gravity,vibrational spectroscopy and XRD data prove that the 4experimental samples are Fluorphosphohedyphane.The present paper is the first report on the discovery of Fluorphosphohedyphane from Chenzhou of Hunan Province,China.This provides an initial spectroscopy analysis on which to undertake further studies of chemical quantitative analysis,composition,or structural refinement work.