Abstract
The chalcocite group minerals are widely distributed among different hydrothermally affected rocks, the oxidized zone of copper sulfide deposits, or may be even crystalline from supersaturated volcanic gases. Some of the chalcocite group minerals form the main Cu orebodies. Djurleite (Cu31S16) is a rare member of the chalcocite group, with a very complex structure. The physical and chemical similarities between all members of the group make them almost unidentifiable by macroscopic and microscopic methods. In this study, Ag-bearing djurleite from the Kupferschiefer deposits, Lower Silesia, Poland, is characterized by EMPA (Electron Microprobe Analyses), XRD (X-Ray Diffraction), and Raman spectroscopy. Djurleite from the investigated site has the following general, average chemical formula: Cu30.86Ag0.1Fe0.04S16. The Ag content is up to 0.55 wt.%, while Fe is up to 0.19 wt.%. The presence of djurleite confirms a low-temperature (~90 °C), hydrothermal origin of the Cu-Ag deposit in Kupferschiefer, which is consistent with previously studies. Moreover, the authors believe that Ag-rich djurleite may often be mistaken for Ag-rich chalcocite, which used to be one of the main Ag-bearing minerals in the orebody from the Cu-Ag deposit in the Fore-Sudetic Monocline. However, the confirmation of such a statement requires more samples, which should be studied in detail.
Highlights
Published: 26 April 2021Djurleite is a copper sulfide with the general chemical formula of Cu31 S16
We present the mineralogical and compositional features of djurleite (Figure 2) in the Kupferschiefer Unit from Lower Silesia in Poland
Following detailed observations using an optical microscope, back-scattered electron imaging (BSE), X-ray powder diffraction (XRD), and Raman spectroscopy, these investigations led to the identification of Ag-rich djurleite, which is commonly not recognized during explorations in the mine
Summary
Djurleite (space group P21 /n, a: 2.690, b: 1.575, c: 1.357 nm, and β: 90.13◦ ) is a copper sulfide with the general chemical formula of Cu31 S16. Djurleite is typically massive in form, but can occur as a thin tabular of prismatic crystals It is a member of the chalcocite group, and is very similar to chalcocite itself (Cu2 S) in its composition and properties, but the two minerals can be distinguished from each other using X-ray powder diffraction (XRD). But in most cases it is in an accessory phase, without economic use as a copper ore It is mostly found in the secondary enrichment zones of copper deposits, associated with other copper sulfides, i.e., chalcocite, bornite, chalcopyrite, or digenite. Ag-bearing djurleite from the Lubin mine (Figure 1) in Poland is described It forms a massive orebody associated with bornite and pyrite. Following detailed observations using an optical microscope, back-scattered electron imaging (BSE), XRD, and Raman spectroscopy, these investigations led to the identification of Ag-rich djurleite, which is commonly not recognized during explorations in the mine. The dark mineral is anhydrite (Anh). (D) The same association in reflected light
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