Zincospiroffite, a new tellurite mineral species from the Zhongshangou gold deposit, Hebei Province, People's Republic of China
2004
Zincospiroffite (Zn2Te3O8), 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 Zn2Te3O8. An electron-microprobe analysis gave the following composition: ZnO 24.57, PbO 1.64, MgO 0.24, TeO2 71.90, minor FeO and SeO2, total 98.89 (in wt.%), corresponding to an empirical formula (Zn1.97Pb0.05Mg0.04Fe0.02)∑ 2.08 (Te2.95Se0.01)∑2.96O8.00 or, ideally, Zn2Te3O8. Powder X-ray diffraction gave only seven lines with weak intensities [ d in A(I)( hkl ): 4.758(w)(110), 3.240(w)(311), 2.928(m)(113), 2.820(w)(204), 2.155(w)(023,511), 1.985(w)(223), 1.599(w)(425), which are similar to those of the synthetic Zn 2Te3O8 (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) (A), β 99.2(3)°, V 764.57(2.52) A3, with Z = 4 and Dcalc = 5.57 g cm−3. With these parameters, a comparison is made of zincospiroffite, synthetic Zn2Te3O8 and spiroffite. The new mineral and its name were approved by the Commission on New Mineral and Mineral Names of International Mineralogical Association (IMA 2002–047). The only polished section was housed under catalogue number M10442 in the collection of the Geological Museum of China.
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