The crystal structure and second world occurrence of the rare selenide brodtkorbite, ideally Cu2HgSe2, are reported in this paper. Brodtkorbite occurs in the Příbram uranium and base-metal ore district, central Bohemia (Czech Republic) as anhedral aggregates up to 150 μm across, in intergrowths with tiemannite and eucairite in a calcite gangue. Other associated minerals include berzelianite, umangite and uraninite. In reflected light, brodtkorbite is cream-white somewhat darker than the associated tiemannite and moderately pleochroic with light pink or bluish tints. Between crossed polarisers, the anisotropy is strong, with violet-grey to yellow-grey rotation tints. Reflectance values in air (Rmin, Rmax in %, λ nm) are 29.4–36.9 (470), 27.8–34.4 (546), 27.2–33.7 (589), 26.4–33.4 (650). Its average composition (14 electron microprobe analyses) is Ag 0.49, Hg 43.08, Cu 23.86, Se 32.25, Te 0.04, S 0.05, total 99.78 wt%. The resulting empirical formula, on the basis 5 atoms per formula unit (apfu), is (Cu1.87Ag0.02)Σ1.89Hg1.07(Se2.03S0.01)Σ2.04. Brodtkorbite is monoclinic, a 7.5048(12), b 4.1851(9), c 8.0131(12) Å, β 124.430 (16)°, V 207.59(8) Å3, space group P21/c, Z = 2. The crystal structure of brodtkorbite was solved by the direct method and refined to R = 8.05% on the basis of 416 unique reflections [I > 3σ(I)] collected on a Rigaku (Oxford Diffraction) SuperNova diffractometer with an Atlas S2 CCD detector and using MoKα radiation. The crystal structure contains one special position of Hg and two general positions of Cu and Se. The crystal structure consists of layers of edge-sharing [CuSe4] distorted tetrahedra where Cu atoms show a 3+1 bond scheme. The [CuSe4] tetrahedra form mackinawite-like layers parallel to (100). The layers show an AA-type of stacking and are connected by linear Se–Hg–Se bonds. Each Cu atom shows three short contacts with three adjacent Cu atoms forming a pseudohexagonal net of metal-metal interactions within one layer. The brodtkorbite crystal structure shows similarities to that of imiterite (Ag2HgS2), but the two minerals are not isostructural.
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Research Article|
August 01, 2017
Brodtkorbite, Cu2HgSe2, from Příbram, Czech Republic: crystal structure and description
Jiří Sejkora;
1
Department of Mineralogy and Petrology, National Museum, Cirkusová 1740, Prague 9 – Horní Počernice 193 00, Czech Republic*
Corresponding author, e-mail: jiri_sejkora@nm.cz
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Pavel Škácha;
Pavel Škácha
1
Department of Mineralogy and Petrology, National Museum, Cirkusová 1740, Prague 9 – Horní Počernice 193 00, Czech Republic2
Mining muzeum Příbram, Hynka Kličky place 293, Příbram VI 261 01, Czech Republic
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František Laufek;
František Laufek
3
Czech Geological Survey, Geologická 6, 152 00 Prague 5, Czech Republic
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European Journal of Mineralogy (2017) 29 (4): 663–672.
Article history
received:
30 Nov 2016
rev-recd:
10 Mar 2017
accepted:
28 Mar 2017
first online:
17 Nov 2017
Citation
Jiří Sejkora, Pavel Škácha, František Laufek, Jakub Plášil; Brodtkorbite, Cu2HgSe2, from Příbram, Czech Republic: crystal structure and description. European Journal of Mineralogy 2017;; 29 (4): 663–672. doi: https://doi.org/10.1127/ejm/2017/0029-2647
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Index Terms/Descriptors
- Bohemia
- cell dimensions
- Central Europe
- chemical composition
- copper
- crystal chemistry
- crystal structure
- Czech Republic
- electron probe data
- Europe
- formula
- gangue
- intergrowths
- mercury
- metals
- optical properties
- physical properties
- pleochroism
- Pribram Czech Republic
- Raman spectra
- refinement
- reflectance
- selenides
- selenium
- spectra
- X-ray diffraction data
- tiemannite
- eucairite
- brodtkorbite
Latitude & Longitude