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ZINCOSPIROFFITE, A NEW TELLURITE MINERAL SPECIES FROM THE ZHONGSHANGOU GOLD DEPOSIT, HEBEI PROVINCE, PEOPLE'S REPUBLIC OF CHINA

2004; Mineralogical Association of Canada; Volume: 42; Issue: 3 Linguagem: Inglês

10.2113/gscanmin.42.3.763

1499-1276

Peng Zhang, Junjie Zhu, Zhuohui Zhao, Xue Ping Gu, Jiayi Lin,

Geochemistry and Geologic Mapping

Zincospiroffite (Zn 2 Te 3 O 8 ), a new tellurite mineral species, was discovered in the Zhongshangou gold deposit in Chongli County, Hebei Province, China.Since it has only been found as crystallite aggregates of hundreds to thousands of micrometers square in a single polished block, most work on the mineral had been carried out under the microscope.This mineral is intimately associated with calaverite and sphalerite, either as micrometric films coating calaverite or in irregular aggregates replacing calaverite.It is a product of secondary co-oxidation of calaverite, associated with sphalerite, pyrite, and other sulfides.It is a gray and translucent mineral, with a dark green streak and a vitreous luster, without internal reflections, and with a weak anisotropy, bireflectance and pleochroism.It is quite soft, has a brittle tenacity and an uneven fracture.Raman spectroscopy demonstrates that the mineral is a natural analogue of synthetic Zn 2 Te 3 O 8 .An electron-microprobe analysis gave the following composition: ZnO 24.57, PbO 1.64, MgO 0.24, TeO 2 71.90, minor FeO and SeO 2 , total 98.89 (in wt.%), corresponding to an empirical formula (Zn 1.97 Pb 0.05 Mg 0.04 Fe 0.02 ) ⌺2.08 (Te 2.95 Se 0.01 ) ⌺2.96 O 8.00 or, ideally, Zn 2 Te 3 O 8 .Powder X-ray diffraction gave only seven lines with weak intensities [d in Å(I)(hkl): 4.758(w)(110), 3.240(w)(31 1), 2.928(m)(113), 2.820(w)(20 4), 2.155(w)(023,511), 1.985(w)(223), 1.599(w)(42 5), which are similar to those of the synthetic Zn 2 Te 3 O 8 (PDF 44-0241).On the basis of the diffraction pattern, the following unit-cell parameters were obtained: a 12.72(4), b 5.15(1), c 11.82(3) (Å), ␤ 99.2(3)°, V 764.57(2.52)Å 3 , with Z = 4 and D calc = 5.57 g cm -3 .With these parameters, a comparison is made of zincospiroffite, synthetic Zn 2 Te 3 O 8 and spiroffite.