我国首次发现的杂铅矿

THE FIRST-TIME DISCOVERY OFIZOKLAKEITE IN CHINA

杂铅矿(Izoklakeite)~[1]是一个Ag-Cu—Pb—Sb—Bi硫盐矿物。1984年发现于我国广西芒场锡—多金属矿床块状锡石—石英—硫化物矿石中。与毒砂、黄铜矿、黝铝矿、方铅矿(少)、浓红银矿和自然铋,有时也与自然锑等密切共生。文中给出了杂铅矿的若干特征参数。

: Izoklakeite is one kind of Cu-Ag-Pb-Sb-Bi Sulfates minerals. It Was found in 1984 in a massive ore of cassiterite-multimetal sulfldes deposite at Mangchang, Guang xi Autonomous Region. The mineral is accompanied by cassiterite, arsenopyrite, pyrite, chalcopyrite, pyrrhotine, pyrite-marcasite, quartz and muscovites. Particularly, and is associated with minerals such as arsenopyrite, stannite chalcopyrite, galena, pyrargyrite and bismuth, and natural Sb sometimes. The mineral was found only in polished section. Its reflected colour is similar to that of galena. It has distinct bireflectance and obvious pleochroism, and has strong anisotropism, parallel extinction, but no internal reflection for mineral powder in oil. Its reflectances in air are 470nm 45.11, 40.77; 550nm 43.27, 39.22; 590nm 42.63, 38.63; 650nm 41.93, 38.07. VHN10= 118.6-130.9kg/mm2. Dcal = 6.58g/cm3, or 6.53g/cm3. The average composition of 20 electron-microprobe analyses gave Pb45.37, Sb12.93 Bi20.78, Ag1.97, Cu1.10, Fe0.18, S17.22, and total amount of these may attain to 99.56 wt%. Based on cations 96 and S114,the analyses yield the following empirical formulae Ag3.77 Cu3.57Fe0.65 Pb45.56 Sb22.03Bi20.66S111.29; with its theoretical correspondent as 2[(Cu.Fe)2 Pb27(Sb. Bi)19 S57]. The unit cell is of orthorhombic symmetry, and the space group is pnnm or pnn2(Harris, 1986), with a= 33.74(1), 6 = 37.99(2), c = 4.063(2)A, K=5208(3)A3. The strongest lines of the x-ray powder diffraction pattern are 3.389(100) (hkl 2MO), 3.290 (45) (451), 3.028 (44) (1120), 2.894 (54) (821), 2.876 (56) (751), 2.823 (42) (81100), 2.141 (43) (5141), 2.027 (46) (7170).