承德矿——有序的天然铁、铱合金的新矿物  

CHENGDEITE--ORDERED NATURAL IRON-IRIDIUM ALLOY

作　　者：於祖相[1] 

机构地区：[1]中国地质科学院地质研究所

出　　处：《地质学报》1995年第3期215-220,T001,共7页Acta Geologica Sinica

基　　金：国家自然科学基金(编号 49172082)

摘　　要：承德矿产在纯橄榄岩铬铁矿体及其邻近的砂矿中,呈粒状、聚粒状与硫铅铜铱矿共生,有的呈文象状与自然铱紧密共生。金属光泽,不透明,钢灰色,粉末黑色。H_M5.2,VHN_(50)452kg/mm^2。无解理,无断口,强磁性。计算密度为19.19g/cm^2。 反射色为亮黄白带淡黄色调,内反射无,均质性,双反射或反射多色性无。 电子探针分析13个数据的平均值(％):S 0.001,Fe 7.9,Ni 0.03,Co 0.03,Cu 0.83,As 0.02,Rh 0.19,Pd 0.00,Os 0.06,Ir 88.5,Pt2.2,Pb 0.00。简化的理论式为Ir_2Fe,理论成分Ir 91.17,Fe 8.83。总量100.00(％)。 5条承德矿最强X光衍射线从hkl,d,I分别为:111,2.18(80);200,1.89(60),220,1.34(70);311,1.142(100);222,1.094(80)。根据X光粉晶指标化,求得承德矿为等轴晶系,空间群:Pm3m,α0.3792(5)nm.V=0.05453(1)nm,Z=1。承德矿样品存放在中国地质博物馆。Chengdeite occurs as a constituent in placer concentrates in a branch of the Luanhe River about 200km NNE of Beijing. It is also found in chromite ores in ultrabasic rocks. Its associated minerals are ferrian platinum, iridium, laurite, chromite, magnetite, gold, galena and isoferroplatium. The mineral may have formed through reaction of inaglyite with ferrian platinum.Chengdeite associated with inaglyite is up to 0.3-0.5mm in grain size, while when it occurs as graphic intergrowths with iridium, it is 0.1-0.5mm. It also occurs as fine grains (5 to 20μm in diameter) separated out from an undescribed mineral with the composition (Fe, Ni, Cu)2IrS3.It is opaque with metallic lustre, colour steel-black, streak black, HM = 5.2, VHN50 = 452 kg/mm2 (range 411-467), malleable, cleavage not observed, fracture not observed, strongly magnetic. Density could not be measured directly because of the small grain size. Density (cal.) = 19.19g/cm3.Its reflection colour is bright white with a yellowish tint. It has no internal reflection, anisotropism, bireflectance or pleochrism.Thirteen chemical analyses were carried out by means of the electron micro-probe using the following standards of pure metals: Fe, Ni, Co, Cu, Rh, Pd, Os, Ir, Pt, and As (PtAs2), Pb (PbS). The mean percentages (and ranges) of these metals are: S 0.001 (0.000-0.008), Fe 7.9 (6.4-8.4), Ni 0.03(0.00-0.08), Co 0.03 (0.00-0.08) Cu 0.83(0.76-0.91), As 0.02 (0.00-0.15), Rh 0.19 (0.07-0.34), Pd 0.00 (0.00-0.04), Os 0.06 (0.00-0.22), Ir 88.5 (86.5-92.3), Pt 2.2 (0.1-3.6) and Pb 0.00 (0.00-0.00). The empirical formula (based on 4 atoms) is: (Ir2.926 Pt0.072 Rh0.012 Os0.002)σ3.012(Fe0.899 Cu0.083 Ni0.003 Co0.003)Σ0.988 .The simplified formula is Ir3Fe, which requires: Ir 91.17 and Fe8.83, the total being 100.00(%).Single crystal X-ray studies could not be carried out because of the small crystal size, but the X-ray powder diffraction data were indexed by analogy with those of isoferroplatium. Five strongest lines of X-ray powder diffraction (hkl, d, I) are: 111,

关 键 词：新矿物 承德矿 铬矿石 铬铁矿 铱合金 

分 类 号：P578[天文地球—矿物学]