新矿物马营矿──铱的碲、铋化物

MAYINGITE──A NEW IRIDIUM BISMUTHIDE-TEHURIDE

马营矿产在纯橄榄岩体内的铝矿体中，在铝矿石及矿体附近的砂矿中均可找到。呈块状聚粒结构，与疏铱矿（IrS2）、双峰矿、高台矿等紧密共生。直径0．02～0．2mm，有的呈脉状。不透明。钢灰色、粉末黑色。金属光泽。HM＝4。VHN50＝178kg／mm2（范围158～241kg／mm2）。无解理和断口，性脆。计算密度为12．77g／cm3。反射色亮白带淡黄色调。无内反射，有光性异常，有弱至中等均质性，但少数有中等非均质性。偏光色淡蓝或淡黄。无双反射与反射多色性。电子探针分析7个数据的平均结果与范围：Cu0．1（0．0～0．2），Te24．6（23．6～25．6），Ir346（322～35．8），Pt1．9（0．3～3．2），Bi38．5（35．9～41．6），总量99．7wt％。实验式根据原子数为3计算：（Ir0.99Pt0.01）Σ1.00Bi0.99Te100简化的理论式为IrBiTe，理论成分：Ir3635，Bi39．52，Te24．13。11条马营矿最强X射线衍射线hkl，d、I为：210，2．89（70）；211，2．65（60）；311，1．955（100）；321，1．735（80）；421，1．417（60）；511，1．250（80）；520，1．207（70）；521，1．186（60）；440，1．148（70）；532，1．054（70）；533，0．9911（70）。根据X射线粉晶指标化，求得马营矿为等轴晶系，空间群：Pα3，α＝0．6502（4）nm，

Mayingite was found as a constituent of placer concentrates and crushed ores of the chromite deposit, near the village of Maying about 230 km NNE of Beijing. Associated minerals are: osmium ferrian platinum, iridisite, laurite, chromite, magnetite, gold, irarsite and shuangfengite.As massive aggregates 0. 02~0. 2 mm in diameter and as veinlets 0. 1~0. 2mm wide and 1. 0 mm long. Opaque with metallic lustre. Colour: steel black. Streak:black. HM= 4. VHN50= 178 kg/mm2 (range 158~ 241). Cleavage: none. Fracture: none. Brittle. Density could not be measured because of small grain size. Density(cal.) = 12. 77g/cm3.Colour: bright white with yellowish tint. Internal reflections: none- Anisotroplsm: none but some what anomalous moderate with blulsh or yellowish tint. Bireflectance and pleochrism:none. Eleven chemical analyses were carried out by means of an electron microprobe using the fol lowing standards; pure metals: Fe,Cu, Rh,Te, Ir, Pt, Bi,sperrylite (As) and galena (Pb ). The mean analytical results (and ranges ) are: Fe-,Cu-, As-, Rh-and Te 24. 6 (23. 6~ 25. 6),Ir 34. 6 (32. 2~35. 8),Pt 1. 9(0. 3~3. 2) and Pb-,Bi 38. 5 (35. 9~ 41. 6), totaling 99. 7 wt%. The empirical formula (based on 3 atoms ) is: (Ir0,99Pt0.01)Σ1.00Bi0.99Te1.00. The simplified formuls is IrBiTe,which requires:Ir 36. 35, Bi 39. 52, Te 24. 13,total 100. 00wt%.Single-crystal X-ray studies could not be carried out because of small crystal size, but the X ray powder diffraction data were indexed on a cubic cell (with systematic absences indicating the space group Pα3) and gave the following data. Eleven strongest llnes hkl,d,I in the X-ray diffraction powder pattern are: 210, 2. 89(70); 211, 2. 65(60); 311, 1. 955(100): 321, 1. 735(80);421,1. 417(60); 511, 1. 250 (80); 520, 1. 207 (70);52l, 1. 186 (60); 440, 1. 148 (70); 532, 1. 054 (70)and 533, 0. 9911 (70). Unit cell data (parameters refined from the powder data ): cubic: Pα3, α =0. 6502(4) nm, V= 0.2749nm3, Z= 4.The mineral is named after its locality. Type material has been deposited at the Geological Museum of China.