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GEOREF RECORD

Hereroite and vladkrivovichevite; two novel lead oxychlorides from the Kombat Mine, Namibia

R. Turner, O. I. Siidra, M. S. Rumsey, S. V. Krivovichev, C. J. Stanley and J. Spratt
Hereroite and vladkrivovichevite; two novel lead oxychlorides from the Kombat Mine, Namibia (in Special issue in honour of Mark D. Welch, principal editor of Mineralogical Magazine from 2007 to 2011, Diego G. Gatta (editor))
Mineralogical Magazine (August 2012) 76 (4): 883-890

Abstract

Two new lead oxychloride minerals, hereroite [Pb (sub 32) (O,&) (sub 21) ](AsO (sub 4) ) (sub 2) ((Si,As,V,Mo)O (sub 4) ) (sub 2) Cl (sub 10) and vladkrivovichevite [Pb (sub 32) O (sub 18) ][Pb (sub 4) Mn (sub 2) O]Cl (sub 14) (BO (sub 3) ) (sub 8) .2H (sub 2) O occur in association with asisite, damaraite, kombatite, sahlinite, copper, quartz, barysilite, Mn silicates and a number of Mn oxyhydroxide minerals on a specimen from the Kombat mine in Namibia. The minerals formed as late-stage products of hydrothermal reworking of primary sulfide minerals. Hereroite is monoclinic, C2/c with a=23.14(1), b=22.65(1), c=12.39(1) Aa, beta =102.00(5) degrees , V=6351.6(41) Aa (super 3) from powder-diffraction data and a=23.139(4), b=22.684(4), c=12.389(2) Aa, beta =102.090(3) degrees , V=6358.8(18) Aa (super 3) from single-crystal data. It is bright orange, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 8.15 g cm (super -3) . The mean refractive index in air at 589 nm is 2.38. The six strongest reflections in the X-ray powder diffraction pattern [d in Aa, (I), (hkl)] are as follows: 2.982(100)(55i1); 2.795(47)(802i); 1.986(24)(88i2i); 1.641(24)(11.5i.5i); 3.512(23)(612i); 3.901(21)(511). Hereroite is named for the Herero people, one of the indigenous tribal groupings in the region where the Kombat mine is located. Vladkrivovichevite is orthorhombic, Pmmn with a=12.87(5), b=27.7(4), c=11.46(3) Aa, V=4080.1(5) Aa (super 3) , from powder-diffraction data and a=12.759(1), b=27.169(4), c=11.515(1) Aa, V=3992.0(9) Aa (super 3) , Z=2, from single-crystal data. It is pale greenish yellow, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 7.40 g cm (super -3) . The mean refractive indices in air at 589 nm are 2.30 and 2.34. The six strongest reflections in the X-ray powder diffraction pattern [d inAa, (I), (hkl)] are as follows: 2.860(100)(370); 2.733(84)(073); 3.707(49)(073); 3.068(37)(401); 2.075(32)(473); 1.601(32)(3.14.3). Vladkrivovichevite is named in honour of Prof. Dr Vladimir Gerasimovich Krivovichev (b. 24.04.1946), Head of the Department of Mineralogy, Geological Faculty, St Petersburg State University. The crystal structures of hereroite and vladkrivovichevite consist of alternating litharge-like O-Pb double layers and chlorine sheets and both are structurally related to other layered lead oxychlorides. In hereroite, tetrahedral AsO (sub 4) and (Si,As,V,Mo)O (sub 4) groups locate in defects within the O-Pb block, which combines square "symesite-type" and double-square "kombatite-type" cavities in its crystal structure. The structure of vladkrivovichevite is based on O-Pb derivative blocks with the interlayer occupied by Cl (super -) anions and oxocentred OPb (sub 4) Mn (sub 2) octahedra whose eight triangular faces are capped by triangular borate anions, BO (super 3-) (sub 3) .


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 76
Serial Issue: 4
Title: Hereroite and vladkrivovichevite; two novel lead oxychlorides from the Kombat Mine, Namibia
Title: Special issue in honour of Mark D. Welch, principal editor of Mineralogical Magazine from 2007 to 2011
Affiliation: The Drey, Allington Track, Allington, United Kingdom
Affiliation: Universita degli Studi di Milano, Milan, Italy
Pages: 883-890
Published: 201208
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 22
Accession Number: 2012-094389
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
S19°43'00" - S19°43'00", E17°43'00" - E17°43'00"
Secondary Affiliation: Saint Petersburg State University, RUS, Russian FederationNatural History Museum, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201249
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