The new mineral species arsenmarcobaldiite, Pb12(As3.2Sb2.8)Σ=6S21, occurs as black anhedral grains, up to 0.5 mm in size, with metallic lustre, associated with pyrite and minor sphalerite, within layers of granoblastic quartz and accessory baryte embedded in pyrite-rich schist from a small baryte + pyrite prospect at Verzalla, Stazzema, Apuan Alps, Tuscany, Italy. Under the ore microscope, arsenmarcobaldiite is white. It is weakly pleochroic in shades of grey. Anisotropy is distinct, both in air and oil, with rotation tints from brownish to bluish-grey. Reflectance percentages for the four COM wavelengths are [Rmin, Rmax (%) (λ)]: 32.8, 38.3 (470 nm); 32.2, 37.5 (546 nm); 31.7, 36.9 (589 nm); 31.4, 36.6 (650 nm). Polysynthetic twinning is common and characteristic. Electron microprobe analysis gave (in wt% – average of 19 spot analyses): Ag 0.20(1), Pb 66.34(38), As 6.36(10), Sb 8.93(9), Bi 0.30(5), S 18.00(14), total 100.13(48). On the basis of ΣMe = 18 atoms per formula unit, the chemical formula is Ag0.07(1)Pb11.96(5)(As3.17(4)Sb2.74(3)Bi0.05(1))Σ5.96S20.97(17), ideally Pb12(As3.2Sb2.8)Σ=6S21. The main diffraction lines, corresponding to multiple hkl indices, are [d in Å (relative visual intensity)]: 3.595 (m), 3.429 (m), 3.214 (ms), 3.027 (ms), 2.233 (s), 2.125 (ms), 1.839 (ms). The X-ray diffraction study gave a triclinic unit cell, space group P, with a = 8.9736(9), b = 29.334(3), c = 8.4925(10) Å, α = 98.369(6), β = 118.705(6), γ = 90.874(6)°, V = 1930.5(4) Å3, Z = 2. The crystal structure was solved and refined to R1 = 0.063 on the basis of 6325 reflections with Fo > 4σ(Fo) and 364 refined parameters. Arsenmarcobaldiite is a new N = 3.5 homologue belonging to the jordanite homologous series and it is the As-dominant isotype of marcobaldiite.
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Research Article|
September 01, 2019
Arsenmarcobaldiite, Pb12(As3.2Sb2.8)Σ=6S21, a new N = 3.5 jordanite homologue from the Sant’Anna tectonic window, Apuan Alps (Tuscany, Italy)
Cristian Biagioni
;
1
Dipartimento di Scienze Della Terra, Università di Pisa
, Via S. Maria 53, 56126Pisa, Italy
Corresponding author, e-mail: cristian.biagioni@unipi.it
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Yves Moëlo
;
Yves Moëlo
2
Institut des Matériaux Jean Rouxel, UMR 6502, CNRS, Université de Nantes
, 2, rue de la Houssinière, 44322Nantes Cedex 3, France
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Stefano Merlino
;
Stefano Merlino
1
Dipartimento di Scienze Della Terra, Università di Pisa
, Via S. Maria 53, 56126Pisa, Italy
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Marco Pasero
;
Marco Pasero
1
Dipartimento di Scienze Della Terra, Università di Pisa
, Via S. Maria 53, 56126Pisa, Italy
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Werner H. Paar
;
Werner H. Paar
3
Department of Chemistry and Physics of Materials, University of Salzburg
, Jakob-Haringer-Strasse 2a, 5020Salzburg, Austria
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Simone Vezzoni
;
Simone Vezzoni
4
Istituto di Geoscienze e Georisorse, CNR
, Via Moruzzi 1, 56124Pisa, Italy
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Federica Zaccarini
Federica Zaccarini
5
Department of Applied Geological Sciences and Geophysics, University of Leoben
, Peter Tunner Str. 5, 8700Leoben, Austria
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European Journal of Mineralogy (2019) 31 (5-6): 1067–1077.
Article history
received:
29 Mar 2019
rev-recd:
15 Jul 2019
accepted:
25 Jul 2019
first online:
16 Sep 2019
Citation
Cristian Biagioni, Yves Moëlo, Stefano Merlino, Marco Pasero, Werner H. Paar, Simone Vezzoni, Federica Zaccarini; Arsenmarcobaldiite, Pb12(As3.2Sb2.8)Σ=6S21, a new N = 3.5 jordanite homologue from the Sant’Anna tectonic window, Apuan Alps (Tuscany, Italy). European Journal of Mineralogy 2019;; 31 (5-6): 1067–1077. doi: https://doi.org/10.1127/ejm/2019/0031-2888
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Index Terms/Descriptors
- antimony
- Apennines
- Apuane Alps
- arsenic
- coordination
- crystal chemistry
- crystal structure
- electron probe data
- Europe
- formula
- homology
- Italy
- jordanite
- lead
- metals
- new minerals
- optical properties
- physical properties
- reflectance
- Southern Europe
- sulfarsenites
- sulfosalts
- Tuscany Italy
- twinning
- windows
- X-ray diffraction data
- Stazzema Italy
- arsenmarcobaldiite
- Verzalla Italy
- Sant'Anna tectonic window
Latitude & Longitude