FAN Chen-zi1, WANG Ling2
(1. National Research Center for Geoanalysis, Beijing 100037, China;
2. College of Mining Engineering, North China University of Science and Technology, Tangshan 063009, China)
Abstract: Ranciéite and chalcophanite are considered as quite rare minerals. In this paper the minerals were firstly described in Xiangguang Mn-Ag Deposit. The morphology, chemical and structure features of natural ranciéite and chalcophanite were characterized by scanning electron microscopy (SEM), electro probe microanalysis (EMPA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectrometry. Both of ranciéite and chalcophanite show needle, rod -like shapes with the sizes varying from nanometers to dozens of micrometers. The XRD of the samples agree with hexagonal structures of the layers along c axis. The Ca2+ or Zn2+ cations in the layer structures of ranciéite and chalcophanite are partly substituted by Mn2+, Mg2+, K+, Na+ and Ag+. The interlayer spacing for ranciéite and chalcophanite decreases from 0.69～0.75 nm to 0.53 nm in TEM which corresponds to the loss of the interlayer water. Chalcophanite features three main Raman scattering contributions at about 606, 651 and 163 cm-1, while ranciéite has one main Raman scattering contribution at about 645 cm-1. The silver is more concentrated in chalcophanite than ranciéite, indicating that the special layer or tunnel structures of manganese oxides have an important effect on the enrichment of silver during the weathering process.
Keywords: ranciéite; chalcophanite; Xiangguang; Mn-Ag deposit; layer structure
Email: czfan2013@163.com
ACTA MINERALOGICA SINICA Vol. 35, No. 4, 2015, Page 522-528
