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Jichengite 3CuIr 2 S 4 ·(Ni, Fe) 9 S 8 , a New Mineral, and Its Crystal Structure
Author(s) -
YÜ Zuxiang,
HAO Ziguo,
WANG Hanggen,
YIN Shuping,
CAI Jianhui
Publication year - 2011
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.2011.00537.x
Subject(s) - pleochroism , mohs scale of mineral hardness , ilmenite , chromite , mineralogy , osmium , crystallography , mineral , magnetite , phlogopite , geology , materials science , crystal structure , geochemistry , chemistry , metallurgy , mantle (geology) , biochemistry , ruthenium , catalysis
A new mineral, jichengite ideally 3CuTr 2 S 4 ·(Ni,Fe) 9 S 8 , was found as a constituent of placer concentrates at a branch of the Luanhe River, about 220 km NNE of Beijing. Its associated minerals are chromite, magnetite, ilmenite, zircon, native gold, iridium, ferrian platinum and osmium. The placer is distributed at places around ultrabasic rock, which hosts chromite orebodies, from which PGM originated. Jichengite occurs commonly as massive or granular aggregates. No perfect morphology of jichengite was observed. It is steel gray and opaque with metallic luster and black streak. It has a Mohs hardness of 5, VHN (d) μm 21.65, H m 4.465, Hv = 268.1 N/um 2 . It is brittle and weakly magnetic. Cleavage {010} is rarely observed. No fracture was observed. Density could not be measured because of its too small grain size. Density (calc.) is 7.003 g/cm 3 . Reflect light is reddish‐brown, without internal reflections. Anisotropism is distinct with grayish or yellowish white in crossed nicols and bluish violet‐copper red in uncrossed nicols. Jichengite shows weak pleochroism and strong bireflectance. The reflectance values in air at the Standard Commission on Ore Mineralogy wavelengths are: 38.9, 34.3 at 470 nm, 38.9, 34.5 at 546 nm, 39.1, 35.3 at 590 nm, 39.2, 36.8 at 650 nm, parallel‐axial extinction. The six strongest lines in the X‐ray powder‐diffraction pattern [d in Å, (I), (hkl)] are: 3.00 (100) (116), 2.80 (50) (205), 2.48. (50) (208), 1.916 (40) (2, 1, 10), 1.765 (60) (220), 1.753 (50) (2, 0, 16). Five chemical analyses carried out, yielding the following results: S 25.76 (25.49–5.97), Fe 10.03 (9.78–10.31), Co 0.78 (0.75–0.81), Ni 12.48 (12.32–12.85), Cu 4.77 (4.69–1.83), Ir 46.98(46.14–17.89), sum 100.80wt%, which produced a formula (Cu 1.556 Fe 0.976 ) 2.532 (Ir 5.063 S 10.126 )·(Fe 2.7451 Ni 4.404 Co 0.273 ) 7.422 S 6.517 . The ideal formula is X 10 Ir 5 S 17.5 , which was calculated by single crystal structure analyses, where X = Cu(II) + Fe(II) + Ni(II) + Co(II). The single crystal data were collected using a diffractometer with Mo Kα radiation and a graphite monochromate. The crystal system is trigonal with space group R3m and unit cell parameters a=7.0745(14) Å, c=34.267(10) Å (The superstructure not found), and the final R Indices [with 564 observed reflections, I>2sigma (I)] are R 1 =0.0495, wR 2 =0.1349. The specimens are deposited in the Geological Museum of China.