摘要
长城矿产在铬铁矿体及临近矿体的铂砂矿中。呈块状聚集体或细脉状,分布在硫铱矿的边缘并交代它。不透明,金属光泽,钢灰色,条痕黑色。莫氏硬度H_M=3.7,显微硬度VHN_(20)=165kg/mm^2。均质性,无解理。计算密度D_(calc.)=11.96g/cm^3。7个电子探针分析的平均化学成分(％):S 7.2,Cu 0.3,Te 0.4,Ir 41.2,Pt 2.8,Bi 47.2,总量99.1。简化的化学式为IrBiS。5条最强X射线粉晶衍射线(hkl,d,I)为:210,2.75(70);211,2.51(60);311,1.860(100);440,1.090(50);600,1.027(50)。X射线粉晶衍射图谱与马营矿相似。进行对比后,长城矿可以指标化为等轴晶系、空间群P2_13。由X射线粉晶衍射线求得α=0.6164(4)nm,V=0.2342nm^3,Z=4。
The mineral occurs in chromite orebodies in dunite and in placers as a constituent of concentrates at a branch of the Luanhe River, about 200 km NE of Beijing. Associated minerals are os-miridium, ferrian platinum, iridisite, laurite, sperrylite, cooperite, irarsite, shuangfengite, mayingite chromite and gold. The mineral is formed hydrothermally and replaces laurite and iridisite. It occurs as massive aggregates 0. 02-0. 2 mm in diameter'and as veinlets 0. 1-0. 2 mm wide and 1. 0 mm long. Opaque with metallic luster colour steel black; streak black; HM = 3.7; VHN20 = 165 kg/nm2(range, 140-185); cleavage; none; fracture: none; brittle. Density can not be measured because of small grain size. Density (calc. ) = 11. 96 g/cm3. Colour bright white with a yellowish tint; internal reflections: none; anisotropism and pleochrism none. Seven chemical analyses were carried out by means of an electron microprope using the following standards.-pure metals (Ni, Cu, Te, Ir, Pt, Bi) and pyrite (S). The mean analytical results (and ranges) (%) are: S 7. 2 (6. 9-8. 1), Ni 0. 0 (0. 0-0.1), Cu 0.3 (0. 2-0.4), Te 0.4 (0. 3-0.7), Ir 41.2 (40.4-42.2), Pt 2.8 (1.8-3.5), Bi 47. 3 (46.4-48.2), total 99. 1(97.2-99.8). The empirical formula (based on 3 atoms) is (Ir0.996Pt0..63Cu0.021) 1.020 (Bi0.986Te0.014)1.000S0.981 The simplified formula is IrBiS, which requires Ir 44. 4, Bi48. 2, S 7. 4, total 100. 0 (%). Single-crystal X-ray studies could not be carried out because of the small crystal size. Changchengite powder patterns are similar to those of mayingite. It could be indexed on a cubic unit cell with a space group P2j3, and after refinement from the powder data we obtain; a = 0. 6164(4) nm and Z = 4. It is named after its locality which is situated near the Great Wall (Changcheng in Chinese).
出处
《地质学报》
EI
CAS
CSCD
北大核心
1997年第4期336-339,共4页
Acta Geologica Sinica
基金
国家自然科学基金资助项目(编号49572095)
关键词
新矿物
长城矿
铂砂矿
铱
硫铋化物
new mineral, changchengite, chromite orebody ,platinum placers
