砷铅铁矾的矿物学特征及其地质环境意义

MINERALOGICAL CHARACTERISTICS OF BEUDANITE AND ITS GEOLOGY ENVIRONMENT SIGNIFICANCE

砷铅铁矾一般产出于含砷硫化物矿床氧化带铁帽中,常见与之共生的矿物有臭葱石、砷铅石、砷铅铁石、乳砷铅铜石等砷酸盐类矿物。该矿物呈菱面体晶体,常呈假立方体状、粒状和球粒状。暗黄绿色。Hm=3.5,Hv=375kg/mm2,Dm=4。广西平桂矿区产出的砷铅铁矾的化学成份w(B)/%为:PbO31.18,Fe2O331.38,As2O518.87,SO310.84,H2O8,据此计算的矿物分子式为:Pb0.99Fe2.80(AsO4)1.17(SO4)0.96(OH)6.24。广西德保矿区产出的含铜较高的铜砷铅铁矾(?)的平均化学成份.w(B)/%为:PbO31.72,Fe2O329.21,CuO7.96,As2O514.84,SO39.88,H2O8,据此计算的矿物分子式为:Pb0.99Fe2.61Cu0.69(AsO4)0.89(SO4)0.86(OH)7.20。砷铅铁矾(德保)的粉晶X射线分析主要衍射强线有:5.90(9),3.65(5),3.07(10),2.29(8),1.976(6)。晶胞参数为:a0=0.732nm,c0=1.702nm,Z=3。三方晶系,空间群为R3m。红外吸收光谱分析显示有波数/cm-1为3475,3402,3212,1639,993,919,825,763,549,535,428等吸收带。差热分析显示有460℃,770℃和910℃3个明显的吸热谷。

Beudanite occurred in the gossan of the oxidized zone of sulfide ore deposit.It was associated with scorodite,mimetesite,garminite,bayldonite.rhombi and usually with pseudo-cube grain and ball-grain in form,dark green-yellow. Hm=3.5,Hv=375 kg/mm^2,Dm=4.The composition of beudanite from Pinggui deposite district was characterized by w_B/%:PbO 31.18,Fe_2O_3 31.38,As_2O_5 18.87,SO_3 10.84,H_2O 8. The chemical formula is Pb_(0.99)Fe_(2.80)(AsO_4)_(1.17)(SO_4)_(0.96)(OH)_(6.24).The composition of Cu-bearing beudanite(?) from the Debao deposite district was characterized by w_B/%:PbO 31.72,Fe_2O_3 29.21,CuO 7.96,As_2O_5 14.84,SO_3 9.88,H_2O 8.The chemical formula is Pb_(0.99)Fe_(2.61)Cu_(0.69)(AsO_4)_(0.89)(SO_4)_(0.86)(OH)_(7.20).The strongest lines in the X-ray powder pattern of the beudanite in the Debao deposite district are 5.90(9),3.65(5),3.07(10),2.29(8),1.976(6).The cell dimemsions are a_0=0.732 nm,c_0=1.702 nm,Z=3.Trigonal system,S.G. R3m.Infra-red spectra show absorption bands at 3 475,3 402,3 212,1 639,993,919,825,763,549,535,428(cm^(-1)).Differential thermal analysis demonstrates endothermal peaks at 460℃,770℃ and 910℃.