汞银黝铜矿Ag6(Cu_(4)Hg_(2))Sb_(4)S_(13)——黝铜矿族新矿物

Argentotetrahedrite-(Hg) Ag;(Cu_(4)Hg_(2))Sb_(4)S_(13):a new tetrahedrite group mineral from the Dongping Hg-Ag deposit,Hunan Province,China

作为黝铜矿族矿物的新成员,汞银黝铜矿(Argentotetrahedrite-(Hg),IMA 2020-079),Ag;(Cu_(4)Hg_(2))Sb_(4)S_(13),发现于湘黔汞矿带北段之保靖东坪Hg-Ag矿床中,是该矿床的主要矿石矿物和回收对象。汞银黝铜矿单晶晶体尺寸约为5~20μm,呈粒径20~300μm的粒状、片状集合体产出,与灰硒汞矿、黑辰砂、含汞自然银、硫锑银矿、辉锑银矿、脆银矿、闪锌矿和方铅矿共生,产于石英、方解石脉中。汞银黝铜矿为黑色,条痕红黑色,金属光泽,无荧光性和磁性,无解理,性脆,断口不规则。矿物的摩氏硬度值为3~3.5,计算密度为5.578 g/cm;。汞银黝铜矿的化学成分:Ag 17.79%;Cu 19.65%;Hg 16.17%;Zn 1.01%;Fe 0.37%;Sb 23.56%;As 0.36%;Se 0.15%;S 20.31%,总量99.52%。依据晶体结构精测和总原子数(29 apfu),得到汞银黝铜矿简化晶体化学式:Ag;(Cu_(4)Hg_(2))Sb_(4)S_(13)。根据1197个衍射点的单晶衍射数据确定了汞银黝铜矿的晶体结构(精修因子R;=0.0294),属立方晶系,空间群为Ⅰ43m,a=1.06330(3)nm,V=1.20217(11) nm^(3),Z=2。其结构中,四面体配位S(1)、八面体配位S(2)和三角锥形配位X(3)分别被S和Sb完全占位。三角形配位M(2)以Ag^(+)(3.39 apfu)和Cu^(+)(2.61 apfu)离子占位,四面体配位M(1)占位离子有Cu^(+)(3.96 apfu)、Hg^(2+)(1.56 apfu)、Zn^(2+)(0.29 apfu)和Fe^(2+)(0.19 apfu),其M(2)位以Ag为主、Hg作为电荷补偿占据M(1)位。

Argentotetrahedrite-(Hg)(IMA 2020-079), Ag;(Cu_(4)Hg_(2))Sb_(4)S_(13)is a new member of tetrahedrite-group of minerals found in the Dongping Hg-Ag deposit, Baojing County, northern section of the Hunan-Guizhou mercury metallogenic belt. It is the main ore mineral and recovery object of the deposit. A single crystal of argentotetrahedrite-(Hg) is around 5~20 μm, and occurs as granular and patchy agglomerate 20 to 300 μm in size. It occurs in association with tiemannite, metacinnabar, mercurian silver, andorite, miargyrite, stephanite, sphalerite and galena in quartz and calcite vein. Argentotetrahedrite-(Hg) exhibits a black colour with a reddish black streak and metallic lustre. The mineral is none fluorescence, magnetism and cleavage, brittle in tenacity, and has irregular fracture. The Morse hardness is 3~3.5. The calculated density is 5.578 g/cm;on the basis of empirical formula and unit cell volume refined from single-crystal XRD data. The chemical composition is Ag 17.79%;Cu 19.65%;Hg 16.17%;Zn 1.01%;Fe 0.37%;Sb 23.56%;As 0.36%;Se 0.15%;S 20.31%, total 99.52%. On the basis of crystal refinement and total atoms=29 apfu, the crystal-chemical formula of argentotetrahedrite-(Hg) is Ag;(Cu_(4)Hg_(2))Sb_(4)S_(13). According to the single crystal diffraction data of 1197 reflections, the crystal structure of argentotetrahedrite-(Hg) is determined(refinement factor R;=0.0294). It is cubic, space group ■ parameters a=1.06330(3) nm, V=1.20217(11) nm^(3), Z=2. In argentotetrahedrite-(Hg), the tetrahedrally coordinated site S(1), the octahedrally coordinated site S(2), and the tri-pyramidally coordinated site X(3) are fully occupied by S and Sb respectively. The triangularly coordinated site M(2) is dominated by Ag;(3.39 apfu) over Cu^(+)(2.61 apfu) and the tetrahedrally coordinated site M(1) is occupied by Cu^(+)(3.96 apfu), Hg^(2+)(1.56 apfu), Zn^(2+)(0.29 apfu), Fe^(2+)(0.19 apfu). It is characterized both by Ag dominance in M(2) and Hg dominance for charge compensation in M(1).