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Tilkerodeite, Pd₂HgSe₃, a New Platinum-Group Mineral from Tilkerode, Harz Mountains, Germany

Ma, Chi and Förster, Hans-Jürgen and Grundmann, Günter (2020) Tilkerodeite, Pd₂HgSe₃, a New Platinum-Group Mineral from Tilkerode, Harz Mountains, Germany. Crystals, 10 (8). Art. No. 687. ISSN 2073-4352.

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Tilkerodeite, ideally Pd₂HgSe₃, is a new platinum-group selenide from the Eskaborner Stollen (Adit Eskaborn) at Tilkerode, Harz Mountains, Germany. Tilkerodeite crystals occur as euhedral inclusions in tiemannite or as extremely fine-grained lamellar aggregates (grain-size up to 3 μm) in a dolomite–ankerite matrix, together with clausthalite, tiemannite, jacutingaite, stibiopalladinite, and native gold. Neighbouring Se-bearing minerals include tischendorfite and chrisstanleyite. Tilkerodeite is opaque with a metallic luster, and is flexible in blade-like crystals, with perfect basal cleavage {001}. In plane-polarized light, tilkerodeite is brownish-grey. It is weakly bireflectant, and weakly pleochroic in shades of light-brown and grey. The anisotropy is weak, with rotation tints in weak shades of greenish-brown and grey-brown. The range of reflectance is estimated in comparison to clausthalite with 45–50%. Electron-microprobe analyses yield the mean composition (wt %) Se 32.68, Hg 26.33, Pt 20.62, Pd 15.89, Pb 2.72, Cu 0.66, S 0.27, total 99.17 wt%. The empirical formula (based on six atoms pfu) is (Pd_(1.08)Pt_(0.76)Pb_(0.09)Cu_(0.07))_(Σ2.00)Hg_(0.95)(Se_(2.98)S_(0.07))_(Σ3.05). The ideal formula is Pd₂HgSe₃. Tilkerodeite is trigonal, with Pt₄Tl₂Te₆-type structure, space group P3–m1, a = 7.325(9) Å, c = 5.288(6) Å, V = 245.7(9) ų, and Z = 2. It is the Pd-analogue of jacutingaite. Tilkerodeite formed hydrothermally, possibly involving the alteration of tiemannite by low-temperature oxidizing fluids. The new species has been approved by the IMA-CNMNC (2019-111) and is named after the locality. Tilkerode is the most important selenide-bearing occurrence in Germany and type locality of naumannite, eskebornite, and tischendorfite.

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Ma, Chi0000-0002-1828-7033
Förster, Hans-Jürgen0000-0002-4654-0382
Additional Information:© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( Received: 27 July 2020; Accepted: 6 August 2020; Published: 8 August 2020. We thank Ritsuro Miyawaki, Chairman of the CNMNC, and its members for helpful comments and edits on the submitted proposal. We thank three reviewers for their constructive reviews. The Caltech GPS Division Analytical Facility, in which the SEM, EBSD, and EPMA analyses were carried out, was partly supported by NSF Grants EAR-0318518 and DMR-0080065. Author Contributions: C.M. performed the SEM, EBSD, and EPMA-WDS analyses and discovered the new mineral. H.-J.F. supervised the research and conducted the EPMA-EDS work. G.G. manufactured the polished sections and took care of the physical and optical data. G.G. was the first who noted the presence of jacutingaite as “unknown” species in the holotype section. H.-J.F., C.M., and G.G. wrote the paper. All authors have read and agreed to the published version of the manuscript. The authors declare no conflict of interest.
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Subject Keywords:tilkerodeite; Pd₂HgSe₃; jacutingaite; Pt₂HgSe₃; palladium; platinum; selenium; new mineral; Tilkerode; Harz Mountains
Issue or Number:8
Record Number:CaltechAUTHORS:20200810-144318893
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Official Citation:Tilkerodeite, Pd₂HgSe₃, a New Platinum-Group Mineral from Tilkerode, Harz Mountains, Germany. Crystals 2020, 10(8), 687;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104895
Deposited By: Tony Diaz
Deposited On:10 Aug 2020 21:50
Last Modified:10 Aug 2020 21:50

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