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Recently formed arsenates from an abandoned mine in Radzimowice (SW Poland) and the conditions of their formation

Siuda Rafał, Januszewska Anna

Acta Geologica Polonica

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2022

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Vol. 72, no. 4

423--442

EN

In the mining galleries of the abandoned Au-As mine in Radzimowice, diverse groups of secondary arsenates crystallized recently. They form several characteristic assemblages. In the first of them the typical minerals are bukovskýite and melanterite. The second group of secondary arsenates includes scorodite, kaňkite, zýkaite, and pitticite. The third assemblage includes Co-Ni-Mg arsenates of the erythrite-annabergite-hörnesite series. The first assemblage crystallized in a zone with a very high activity of sulphate and arsenate ions and where the pH varies within a narrow range of 2.0-3.5. The second group of secondary arsenates formed in the acidic zone. The minerals identified here suggest pH variation within fairly wide ranges, from about 2.0 to 5.5. Contrary to the first and second mineral assemblage, the Co-Ni-Mg arsenates formed under different geochemical conditions. Their crystallization took place under weak acidic to neutral conditions.

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The Rietveld refinement studies of pyromorphite-vanadinite and mimetite-vanadinite solid solution series

Solecka U., Zelek S., Bajda T.

Geology, Geophysics and Environment

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2016

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Vol. 42, no. 1

127--128

EN

Mimetite Pb 5 (PO 4 ) 3 Cl, vanadinite Pb 5 (VO 4 ) 3 Cl and pyromorphite Pb 5 (PO 4 ) 3 Cl belong to the apatite supergroup. They form in oxidation zones of lead ore deposits. These minerals have high thermal stability (Dong et al. 2002) and low solubility (Flis et al. 2011) thus they have many applications. Pyromorphite and mimetite are especially used to immobilize lead in contaminated soils and hazardous industrial wastes (Ma et al. 1993, Kim et al. 2005, Bajda et al. 2007), it is therefore important to know the impact of various factors on their properties. Crystal structure of apatites corresponds to the general formula M 5 (TO 4 ) 3 X, where M are bi - valent cations distributed on two distinct crystallographic sites, TO 4 is a trivalent oxyanion and X is a monovalent anion. The structure and chemistry of apatite allow for numerous substitutions of metal cation and anionic complexes (Hughes & Rakovan 2002, Pan & Fleet 2002). It was found that substitutions cause variations in the unit cell parameters and chemical properties of these minerals (Botto et al. 1997), but there are no articles presenting variations in the whole series. Therefore, these researches present changes of lattice parameters for pyromorphite-vanadinite and mimetite-vanadinite solid solution series. Pyromorphite, mimetite and vanadinite crystallize in hexagonal symmetry (the space group P6 3 /m) (Dong et al. 2002, Pan & Fleet 2002). They form continuous isomorphic series. The aim of study was to examine how lattice parameters of pyromorphite-vanadinite and mimetite-vanadinite solid solutions series change with increasing vanadium content and characterize these pheno mena. Crystallographic studies were conducted on synthetic pyromorphite, mimetite and vanadinite and minerals with intermediate compositions Pb 5 (TO 4 ) 3 Cl, where T = P + V or As + V, of various P/V or As/V ratios. Samples were analyzed by X-Ray diffraction (XRD) using RIGAKU Smartlab X-Ray diffractometer with Cu radiation in a 10° to 110° 2Θ range at a step size of 0.02 2Θ and a rate of 2 s per step. The phase identification was carried out using the X’Rayan computer program and X-ray standard patterns in the form of ICDD files (card 19-0701, 19-0683 and 43-1461). The unit-cell refinement and Rietveld structure refinement were made using the FullProf Suite computer program package (Rodriguez-Carvajal 1993). The Rietveld refinement has shown systematic changes in unit cell parameters of studied samples depending on their chemical composition. Dimensions of unit cell parameters of pyromorphite-vanadinite solid solution series increase linearly with the substitution of vanadate ions in the structure of pyromorphite. Lattice parameter “a” increase in the range of 9.987–10.325 Å, while lattice parameter “c” increase in the range of 7.33–7.343 Å. In case of the mimetite-vanadinite solid solution series, lattice parameter “a” increase (10.251–10.325 Å range), whereas lattice parameter “c” decrease (7.442–7.343 Å range) linearly with the substitution of vanadate ions in the structure of mimetite. This situation indicates the equivalent position of the tetrahedral TO 4 in the structure of lead apatite.

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The philipsbornite–segnitite solid-solution series from Rędziny, eastern metamorphic cover of the Karkonosze granite (SW Poland)

Gołębiowska B., Włodek A., Pieczka A., Borkiewicz O., Polak M.

Annales Societatis Geologorum Poloniae

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2016

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Vol. 86, No. 1

73--83

EN

Supergene minerals of the philipsbornite–segnitite series, PbAl3(AsO4)(AsO3OH)(OH)6–PbFe3+3(AsO4) (AsO3OH)(OH)6, accompanied by carminite, PbFe3+2(AsO4)2(OH)2, were found in relics of hydrothermal quartz– chlorite–arsenopyrite veins, associated with subordinate polymetallic ores disseminated in contact zones of a dolomitic marble deposit at Rędziny, Western Sudetes, Poland, and recognized by means of electron microprobe and X-ray and electron-back-scattered diffraction (XRD and EBSD). Philipsbornite and segnitite, as the two minerals of the series, exhibit highly variable compositions, especially in terms of the range of Fe3+ Al3+ substitution at the G site, with a distinct gap between the values of 0.52 and 0.89 for the Fe/(Al+Fe) ratio; substitutions at the D and T sites are less important. In this respect, the minerals are almost identical with philipsbornite and segnitite, known from other localities. The gap might be a consequence of the limited miscibility of the end-members, but also might be attributed to crystallization under the changing and distinctly differing activities of Al3+ and Fe3+. The unit-cell parameters of philipsbornite, a = 7.1245(13) Ο, c = 17.0967(45) Ο, make the mineral comparable with philipsbornites from other occurrences. The EBSD analysis confirmed the rhombohedral structure of both minerals and the space group symmetry R-3m. The minerals crystallized in the sequence: philipsbornite -> segnitite -> carminite, which reflects (i) decreasing acidity in the oxidation zone, due to the leaching of sulphate ions and interaction of the solutions with a nearby dolomite lens, and (ii) varying activities of Al3+, Fe3+ and Pb2+ cations, mobilized by the solutions through interaction with the silicate host containing disseminated arsenopyrite and subordinate sulphides, up to complete Pb2+ depletion.

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Structural and vibrational behaviour of pyromorphite-vanadinite solid solution series

Solecka U., Bajda T., Topolska J., Manecki M.

Geology, Geophysics and Environment

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2015

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Vol. 41, no. 1

135--136

EN

Pyromorphite Pb5(PO4)3Cl and vanadinite Pb5(VO4)3Cl belong to the apatite supergroup. They are secondary minerals formed in the oxidation zones of lead ore deposits. Both crystallize in hexagonal symmetry with the space group P63/m (Dong et al. 2002). The crystal structure of these two minerals allows to accommodate both metal cations and anionic complexes. It is the reason, why pyromorphite and vanadinite forms solid solution series. Isovalent replacement of P with V is one of the most common anionic substitution. Lead apatites are one of the least soluble along apatites group minerals and characterized by high thermal stability (Dong et al. 2002, Flis et al. 2011). Characteristic properties of apatite structure cause that these minerals are successfully used in many fields, especially for the immobilization of toxic waste and lead-contaminated soil (Ma et al. 1993, Chen et al. 1997, Dong et al. 2002, Kim et al. 2005). So far, pyromorphite and mimetite are the most known and used for the immobilization of lead. Pyromorphite and mimetite are isostructural with vanadinite, therefore it has been predicted that this mineral is also important for the environment. Accordingly, the aim of this study was to characterize of the pyromorphite-vanadinite solid solution series. This research presents systematic changes in the structure of these minerals. Pure pyromorphite and vanadinite and minerals with intermediate compositions Pb5(TO4)3Cl, where T = P + V, of various P/V ratios were synthesized from aqueous solutions at 298 K and pH = 3.5. Synthetic solids were analyzed by X-Ray diffraction (XRD), infrared absorption spectroscopy (FTIR) and Raman spectroscopy. Based on the X-Ray analysis, it was found that synthetic precipitates represent homogeneous phases of pyromorphite and vanadinite, which have intermediate chemical composition. Diffraction peaks of pyromorphite-vanadinite solid solution series were shifted due to replacement of PO4 by VO4. Replacement of PO4 by VO4 anions is causing changes in the structure of apatite and hence these shifts. Unit cell parameters of studied solid solutions show a linear variation. In the FTIR and Raman spectra of pyromorphite-vanadinite solid solutions series, the bands which are characteristic for vibrations of P-O bonds of the PO4 tetrahedra as well as vibrations of V-O bonds of the VO4 tetrahedra appeared. Analysis of Mid-IR spectra and Raman spectra also allowed observing correlation between the band positions and the extent of the anionic substitution among the studied series. The structure of pyromorphite and vanadinite is generally similar, although the two minerals vary in chemical composition. This variability results probably from the properties of individual ions.

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Optimization of synthesis conditions of pyromorphite-vanadinite and mimetite-vanadinite solid solution series

Janicka U., Bajda T., Topolska J., Manecki M.

Geology, Geophysics and Environment

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2014

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Vol. 40, no. 1

88

EN

Minerals: pyromorphite Pb5(PO4)3Cl, mimetite Pb5(As04)3Cl and vanadinite Pb5(VO4)3Cl belong to the apatite supergroup. Commonly they form in hypergenic conditions. They are best known from the oxidation zones of lead ore deposits. Natural pyromorphite usually contains admixture of arse-nates or vanadates, whereas mimetite or vanadinite contain admixtures of phosphates. Solid solutions of the pyromorphite-mimetite series are well known, while the knowledge about anionie substitutions in vanadinite is incomplete. Therefore, the aim of this study was to find optimal conditions for the synthesis of pyromorphite-vanadinte and mimetite-vanadinite solid solution series. This research will allow to check the range of possible anionie substitutions, formation conditions such as pH, temperature and in, turn, to obtain better knowledge about the properties of these minerals. Pyromorphite, mimetite, vanadinite and pyromorphite-vanadinite and mimetite-vanadinite solid solutions series were synthesized from aqueous solutions. Solutions containing Pb2+, PO43-, AsO43-, VO3- , VO43- and Cl- ions in stoichiometric molar proportions were dropwise mixing. This method of synthesis allows controlling the stoichiometry of the chemical composition of synthetic precipitates. Synthesis reactions were carried out at various pH and at different temperatures (range from 25°C to 85°C). After the synthesis, suspensions were left for two weeks for aging. Then the suspensions were filtered using a Biichner funnel. The precipitates were washed with double-distilled water and acetone, and then dried. Synthetic precipitates were analyzed using various analytical techniques including X-Ray diffraction (XRD), Scanning electron microscopy coupled with Energy Dispersive Spectroscopy (SEM/EDS), Infrared absorption spectroscopy (FTIR) and Raman spectroscopy. Results of XRD, SEM/EDS, FTIR and Raman spectroscopy analyzes of studied samples showed that temperature 25°C and pH = 3.5 are optimal conditions to synthesize pyromorphite-vanadinite and mimetite-vanadinite solid solution series. Chervetite Pb2V2O7 was formed together with studied phases at lower pH values (1.7, 2.2), or higher temperatures (75°C, 85°C). At pH = 11.5, minerals with hydroxyl groups were formed. It has been observed that the formation of pyromorphite-vanadinite and mimetite-vanadinite solid solution series mainly depends on the pH values. The temperature is less important.

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Halogen substitution in synthetic lead apatite compounds Raman spectroscopy study

Witkowska M., Motyka J., Kwaśniak-Kominek M., Manecki M.

Geology, Geophysics and Environment

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2014

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Vol. 40, no. 1

141--142

EN

Mimetite Pb10(AsO4)6Cl2, vanadinite Pb10(VO4)6Cl2 and pyromorphite Pb10(PO4)6Cl2 are minerals isostructural with apatite occurring in the oxidation zones of Pb deposits. They exhibit hexagonal structure and rod-shape morphology. To date, most published research on crystal chemistry of lead apatites concentrated on cationic substitutions in crystalline structure (Ca, Pb, Sr etc.). Little is known, however, on anionic solid solutions, particularly on systematic changes in the structure and properties due to halogen substitutions in lead apatites. Precipitation of lead apatites is often used for immobilization of toxic forms of Pb and As in the environment. More recently, immobilization of radioactive isotope 129I in the form of lead apatites was proposed. This isotope is released as a result of accidents at nuclear power plants (Zhang et al. 2007, Stennet et al. 2011, Redfern et al. 2012). Halogen varieties of lead apatites are also used in chemical engineering as environmentally friendly catalysts (Masaoka & Kyono 2006). The objective of this project was synthesis of halogen-substituted lead apatites in pyromorphite series Pb10(PO4)6(F, Cl, Br, I)2, mimetite series Pb10(AsO4)6(F, Cl, Br, I)2, and vanadinite series Pb10(VO4)6(F, Cl, Br, I)2, followed by characteristics of X-ray diffraction patterns and Raman spectra. This will contribute to our knowledge on mechanisms and effects of anionie substitutions in this group of mineral phases. Based on the literature and pilot experiments we developed an efficient method of synthesis of Pb apatite solid solutions which allows for full control on stoichiometry, and results in crystalline, homogeneous precipitate. Lead apatites were synthesized at room temperatures from aqueous solutions of Pbq , phosphates/arsenates/vanadates, and Faq, Claq, Braq, or Iaq solutions mixed in stoichiometric proportions. Solutions are mixed dropwise in large (2 dm3) reactor with distilled water. Suspension is left for 48 hours for aging, filtered and air-dried. X-ray powder diffraction is used for identification of solid phases. Qualitative analysis allows also for identification of systematic shifts in diffraction patterns resulting from halogen substitutions. Calculation of lattice parameters is used to quantify the systematic effects of substitutions on unit cell dimensions. For the first time Raman spectroscopy was applied to most of crystalline phases in question. Analysis of systematic spectral shifts with anionic substitutions was performed which allowed for explanation of molecular structural reasons for spectral shifts as well as for development of identification procedures with the use of Raman spectroscopy. All phases preserve their hexagonal crystalline structure. Both diffraction patterns and Raman spectra corresponding to each synthesized phases exhibit systematic shifts in the series. The most pronounced features on Raman spectrum are shifts of double bands resulting from phosphate stretching mode from 968/932 through 945/918 to 941/910 cm-1 for F, Cl and Br substituted pyromorphites, respectively. Similar trends are observed for mimetite and vanadinite series. These shifts progress towards lower angles 2Θ in XRD patterns and lower Raman shifts on the spectra which is consistent with the increasing ionic radius and atomic mass of the elements resulting in larger unit cell and more rigid chemical bonds. These results confirm that solid-solutions between these phases are possible and result in systematic changes in the structure and spectroscopic properties.