Grootfonteinite, Pb3O(CO3)2, is a new Pb oxycarbonate found in a mineralogically complex, banded assemblage from the Mn(-Fe) oxide ore unit of the Kombat mine. Grootfonteinite is named after the locality in the Grootfontein district. The mineral forms platy grains up to 1 mm across and up to 0.2 mm thick included in and intergrown with massive cerussite. Grootfonteinite is colourless, with white streak and adamantine lustre. It is brittle with perfect cleavage on (0 0 1). The density calculated using the empirical formula H0.345Na0.275Ca0.045Pb2.645C2O7 is 6.856 g · cm−3.The strongest five reflections in the X-ray powder-diffraction pattern [(d in Å)-(Intensity)-(hkl)] are: 4.586-25-0 1 0, 3.244-100-0 1 3, 2.652-30-1 1 0, 2.294-21-0 2 0, 2.053-39-0 2 3. Grootfonteinite crystallizes in space group P63/mmc (No. 194), a = 5.303(1), c = 13.770(3) Å, V = 335.3(1) Å3, Z = 2. The crystal structure of grootfonteinite is formed by layered blocks which consist of sheets with composition [PbCO3] and (ideally) [PbO], the stacking of which can be described as …-[PbCO3]-[PbO]-[PbCO3]-… The composition of the resulting electroneutral 2D block is {[Pb2(CO3)2][(Pb0.7Na0.3)(O0.7(OH)0.3)]}0. The stereochemically active 6s2 lone electron pairs of the two Pb atoms are located in between the blocks, resembling the classical case of the structure of litharge. Grootfonteinite is structurally related to hydrocerussite, abellaite, and plumbonacrite. A characteristic structural feature of all these minerals is the presence of [PbCO3]0 sheets in the upper and lower parts of invariably electroneutral 2D blocks, the middle part being variable. The topology of 2D blocks in the crystal structure of grootfonteinite can be considered as intermediate between those of abellaite and hydrocerussite. These three minerals can be considered to form a merotype family. Other members of this family can be hypothesized which differ in the nature of the interleaved sheets.
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Research Article|
March 01, 2018
Grootfonteinite, Pb3O(CO3)2, a new mineral species from the Kombat Mine, Namibia, merotypically related to hydrocerussite
Oleg I. Siidra;
1
Department of Crystallography, St. Petersburg State University
, University emb. 7/9, 199034St. Petersburg, Russia
Corresponding author, e-mail: o.siidra@spbu.ru
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Erik Jonsson;
Erik Jonsson
3
Geological Survey of Sweden, Department of Mineral Resources
, Box 670, 75128Uppsala, Sweden
4
Department of Earth Sciences, Uppsala University
, 75236Uppsala, Sweden
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Nikita V. Chukanov;
Nikita V. Chukanov
5
Institute of Problems of Chemical Physics
, Chernogolovka, Moscow region, 142432, Russia
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Diana O. Nekrasova;
Diana O. Nekrasova
1
Department of Crystallography, St. Petersburg State University
, University emb. 7/9, 199034St. Petersburg, Russia
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Igor V. Pekov;
Igor V. Pekov
6
Faculty of Geology, Moscow State University, Vorobievy Gory
, 119991, Moscow, Russia
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Wulf Depmeier;
Wulf Depmeier
7
Institut für Geowissenschaften der Universität Kiel
, Olshausenstr. 40, Kiel24098, Germany
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Yury S. Polekhovsky;
Yury S. Polekhovsky
8
Department of Mineral Deposits, St. Petersburg State University
, University emb. 7/9, 199034St. Petersburg, Russia
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Vasiliy O. Yapaskurt
Vasiliy O. Yapaskurt
6
Faculty of Geology, Moscow State University, Vorobievy Gory
, 119991, Moscow, Russia
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European Journal of Mineralogy (2018) 30 (2): 383–391.
Article history
received:
01 Apr 2017
rev-recd:
17 Jun 2017
accepted:
27 Jun 2017
first online:
14 Aug 2018
Citation
Oleg I. Siidra, Erik Jonsson, Nikita V. Chukanov, Diana O. Nekrasova, Igor V. Pekov, Wulf Depmeier, Yury S. Polekhovsky, Vasiliy O. Yapaskurt; Grootfonteinite, Pb3O(CO3)2, a new mineral species from the Kombat Mine, Namibia, merotypically related to hydrocerussite. European Journal of Mineralogy 2018;; 30 (2): 383–391. doi: https://doi.org/10.1127/ejm/2018/0030-2723
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Index Terms/Descriptors
- Africa
- carbonates
- cerussite
- chemical composition
- coordination
- crystal chemistry
- crystal structure
- formula
- infrared spectra
- intergrowths
- manganese
- metals
- mineral cleavage
- Namibia
- new minerals
- optical properties
- oxides
- physical properties
- Southern Africa
- space groups
- spectra
- X-ray diffraction data
- Kombat Mine
- hydrocerussite
- Grootfontein Namibia
- Otjozondjupa Namibia
- oxycarbonates
- grootfonteinite
- abellaite
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