红河石Ca_(18)(□,Ca)_2Fe^(2+)Al_4(Fe^(3+),Mg,Al)_8(□,B)_4BSi_(18)O_(69)(O,OH)_9——符山石族新矿物  

Hongheite Ca_(18)(□,Ca)_2Fe^(2+)Al_4(Fe^(3+),Mg,Al)_8(□,B)_4BSi_(18)O_(69)(O,OH)_9:a new vesuvianite group mineral from the world-class Gejiu tin polymetallic orefield,Yunnan Province,China

作　　者：徐金沙[1] 李国武[2] 范光[3] 葛祥坤[3] 祝向平[1] 沈敢富 XU Jinsha;LI Guowu;FAN Guang;GE Xiangkun;ZHU Xiangping;SHEN Ganfu(Chengdu Geological Survey Center,China Geological Survey,Chengdu,610082;Laboratory of Crystal Structure,China University of Geosciences (Beijing),Beij ing ,100083;Beijing Research Institute of Uranium Geology,Beijing,100029)

机构地区：[1]中国地质调查局成都地质调查中心,成都610082 [2]中国地质大学(北京)晶体结构实验室,北京100083 [3]核工业北京地质研究院,北京100029

出　　处：《地质学报》2019年第1期138-146,共9页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40672025)资助成果

摘　　要：作为符山石族矿物的新成员,红河石(Hongheite,IMA 2017-027新矿物),Ca18(,Ca)2Fe2+Al4(Fe3+,Mg,Al)8(,B)4BSi18O69(O,OH)9发现于个旧世界级Sn-多金属矿田东北缘、与马拉格Sn矿床毗邻的北沙冲花岗岩(77.43Ma)内矽卡岩中。红河石常呈横径达4~25mm的放射状针-柱状集合体产出。当位于晶洞中时,红河石则呈发育良好的自形柱状晶体(0.5~4.0mm长,0.3~1.0mm宽)产出。与红河石共生的矿物见有赛黄晶、萤石、斧石-(Fe)、硅硼钙石、枪晶石、硼锡钙石、石英和羟鱼眼石-(K)等。红河石为墨绿色,条痕浅灰绿色,玻璃光泽,性脆,断口不规则。主要的晶面是:{100}、{110}、{101}和{001}。红河石的显微硬度:988.3N/mm2,相当于摩氏硬度6~7。其实测密度与计算密度分别是3.446g/cm3和3.423g/cm3。红河石一轴正晶,No=1.720(2),Ne=1.725(2);多色性弱。红河石的化学成分:SiO235.85%;TiO20.01%;Al2O311.00%;Fe2O37.92%;FeO2.14%;CaO 33.57%;MnO 0.42%;MgO 3.48%;B2O32.82%;Cr2O30.01%;Na2O 0.01%;F 0.40%(F≡O-0.17);Cl 0.14%(Cl≡O-0.03);H2O 0.75%,总量98.32%。依据晶体结构精测和Si在单位分子式中的原子数(即Si=18 apfu),计算和书写的红河石简化晶体化学式:Ca18(,Ca)2Fe2+Al4(Fe3+,Mg,Al)8(,B)4BSi18O69(O,OH)9。其三条最强粉晶线[d(?)(I/I0)(hkl)]为:2.9289(47)(004),2.7661(100)(342)和2.6079(68)(243)。红河石属四方晶系,空间群为P4/nnc,晶胞参数:a=15.667(3)?,c=11.725(1)?,V=2878(1)?3,Z=2。红河石晶体结构精测的R因子为0.063。红河石殊异于为已知的符山石族矿物种,在于其X(4)位以空位()为主、Y(3)位以Fe3+居优和T(2)位被B所占。顺便对符山石族矿物晶体-化学式的计算与书写予以讨论并提出建议。Hongheite(IMA 2017-027),Ca18(□,Ca)2Fe^2+Al4(Fe^3+,Mg,Al)8(□,B)4BSi18O69(O,OH)9 is a new menber of vesuvianite-group minerals found in the endoskarn of the Baishanchong granite(77.43 Ma)that is adjacent to the Malage skarn Sn deposit,located at the northeast border of the world-class Gejiu tin polymetallic ore-field,Yunnan Province,southwest China.It occurs mostly as radiating acicular to prismatic aggregates 4 to 25 mm in diameter.When the mineral occurs in vugs,their well-formed,euhedral and prismatic crystals are 0.5 to 4.0 mm long and 0.3 to 1.0 mm thick,respectively.Associated minerals include danburite,fluorite,axinite-(Fe),datolite,cuspidine,nordenski9 ldine,quartz and hydroxylapophyllite-(K)etc.Hongheite exhibits a dark green colour with a pale greyish green streak and a vitreous lustre.The mineral is translucent and brittle in tenacity,and has irregular fracture.Dominant crystal forms are {100},{110},{101}and {001}.The microhardness is 988.3 N/mm2,equivalent to Mohs hardness 6~7.The specific gravitiy is Dmeas=3.446 g/cm3 and Dcalc=3.423 g/cm3 respectively.The mineral is optically uniaxial(+)withω=1.720(2),ε=1.725(2)(inwhite light).Its pleochroism is weak.The chemical composition is:SiO235.85%;TiO20.01%;Al2 O3 11.00%;Fe2 O3 7.92%;FeO2.14%;CaO 33.57%;MnO 0.42%;MgO 3.48%;B2O3 2.82%;Cr2 O3 0.01%;Na2O 0.01%;F0.40%;Cl 0.14%;(Cl,F≡O-0.20);H2 O 0.75%total 98.32%.On the basis of crystal refinement and Si=18 apfu,the crystal-chemical formula of hongheite is Ca18(□,Ca)2Fe2+Al4(Fe3+,Mg,Al)8(□,B)4BSi18O69(O,OH)9.The three strongest powder X-ray diffraction lines[din■(I/I0)(hkl)]are:2.9289(47)(004),2.7661(100)(342)and 2.6079(68)(243).The mineral is tetragonal,space group P4/nnc,unit-cell parameters a=15.667(3)■,c=11.725(1)■,V=2878(1)■3,Z=2.The crystal structure has been refined to R=0.063.Hongheite is defined as a new member of the vesuvianite group with Fe3+and B as a dominant cation at the Y(3)and T(2)site separately.By the way,the paper discusses and proposes to revise the current crystal-chemica

关 键 词：红河石 新矿物 符山石族 晶体结构 个旧锡矿 

分 类 号：P578.948[天文地球—矿物学]