This page has only limited features, please log in for full access.
Mining activity in Algares (Aljustrel Mine, Portuguese sector of the Iberian Pyrite Belt, IPB) stems prior to Roman times. As the orebody is vertical and relatively thin, mining was carried out mainly along underground adits (galleries). Nowadays, the deposit is considered exhausted and the area is being rehabilitated for a different use. The Algares +30 level adit intersects two volcanic units of the IPB Volcano-Sedimentary Complex. The massive sulphide and related stockwork zone are hosted by the Mine Tuff volcanic unit and are exposed in the walls of the gallery, showing intense hydrothermal alteration. Along the mine adit, the geological sequence is affected by strong oxidation and supergene alteration, giving rise to the formation of secondary minerals through the oxidation of the sulphides. The most common minerals found were melanterite (FeSO4·7H2O) and chalcanthite (CuSO4·5H2O), forming essentially massive or crystalline aggregates, ranging from greenish to bluish colours. Melanterite from the walls revealed to be Cu-rich by opposition to that from stalactites/stalagmites formed below the old ore storage silo revealing the low-copper-grade ores exploited underground. The mineralogy of the efflorescent salts was used to ascertain the processes involved in their formation, and moreover, the inventory of minerals is presented, as well as their principal characteristics.
Teresa Silva; João Matos; Daniel De Oliveira; João Veiga; Igor Morais; Pedro Gonçalves; Luís Albardeiro. Mineral Inventory of the Algares 30-Level Adit, Aljustrel Mine, Iberian Pyrite Belt, Portugal. Minerals 2020, 10, 853 .
AMA StyleTeresa Silva, João Matos, Daniel De Oliveira, João Veiga, Igor Morais, Pedro Gonçalves, Luís Albardeiro. Mineral Inventory of the Algares 30-Level Adit, Aljustrel Mine, Iberian Pyrite Belt, Portugal. Minerals. 2020; 10 (10):853.
Chicago/Turabian StyleTeresa Silva; João Matos; Daniel De Oliveira; João Veiga; Igor Morais; Pedro Gonçalves; Luís Albardeiro. 2020. "Mineral Inventory of the Algares 30-Level Adit, Aljustrel Mine, Iberian Pyrite Belt, Portugal." Minerals 10, no. 10: 853.
Topsoils developed in different geological formations/ages, and the top layer of the lava flow from the most recent eruption (2014/2015) of Fogo Island (Cape Verde archipelago), were studied. The specific objectives of this work are: i) to estimate the REE contents and patterns in the whole sample of topsoils developed on different geological formations/ages and their correlation with the iron speciation; and ii) to study the top layer of a lava flow from the most recent eruption after two years of exposure. REE contents are in general higher in the topsoils of the pre-caldera than in those developed on the post-caldera formation, particularly the light REE probably due to their incorporation into hematite. Positive Eu anomalies found in recent topsoils suggest the existence of hydrothermal processes with intrusion of hot fluids with higher concentration of Eu2+. In the top layer of the lava flow of the most recent eruption, Fe is incorporated in pyroxenes and iron oxides (magnetite and/or maghemite). This study can be a benchmark for further knowledge of the chemical evolution and weathering rate in semi-arid climate of Fogo Island.
Rosa Marques; Bruno J.C. Vieira; M. Isabel Prudêncio; João Carlos Waerenborgh; M. Isabel Dias; Dulce Russo; Fernando Rocha; Teresa Silva; Francisco Ruiz. Geochemistry and Fe speciation in active volcanic environments – the case of Fogo Island, Cape Verde. E3S Web of Conferences 2019, 98, 06009 .
AMA StyleRosa Marques, Bruno J.C. Vieira, M. Isabel Prudêncio, João Carlos Waerenborgh, M. Isabel Dias, Dulce Russo, Fernando Rocha, Teresa Silva, Francisco Ruiz. Geochemistry and Fe speciation in active volcanic environments – the case of Fogo Island, Cape Verde. E3S Web of Conferences. 2019; 98 ():06009.
Chicago/Turabian StyleRosa Marques; Bruno J.C. Vieira; M. Isabel Prudêncio; João Carlos Waerenborgh; M. Isabel Dias; Dulce Russo; Fernando Rocha; Teresa Silva; Francisco Ruiz. 2019. "Geochemistry and Fe speciation in active volcanic environments – the case of Fogo Island, Cape Verde." E3S Web of Conferences 98, no. : 06009.
The last eruption of the Fogo volcano, in the Cape Verde Archipelago, occurred in 2014–2015. A mineralogical and chemical study was undertaken on fumarole incrustations resulting from this event and compared with results obtained from the previous 1995 eruption. The mineralogical constitution of the fumarole deposits was assessed by X-ray diffraction and the chemical characterization was performed through X-ray fluorescence spectrometry with a wavelength dispersive system and by energy dispersive X-ray fluorescence at the European Synchrotron Radiation Facility. The most common compounds/minerals in solid deposits were sulfur, sodium chloride, and calcium sulphates with variable degrees of hydration, sodium sulphate, hydrated sulphates of sodium aluminum, potassium magnesium, or sodium magnesium and a fluorine-bearing mineral. Thenardite (Na2SO4) and its polymorph (phase III) were found simultaneously for the first time in incrustations, to the best of our knowledge. A large span of minor and trace elements present in incrustations (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ba, Ce, Tl, Pb) were also identified, some of them potentially hazardous to animal and human health. This study reveals that low temperature incrustations, allied to the atmospheric conditions of Fogo volcano, constitute a natural laboratory to observe the process of mineral formation—namely the Na2SO4 phase III considered metastable.
Teresa P. Silva; Daniel P. S. De Oliveira; João Pedro Veiga; Paula Ávila; Carla Candeias; Eduardo Salas Colera; Rita Caldeira. Mineralogy and chemistry of incrustations resulting from the 2014–2015 eruption of Fogo volcano, Cape Verde. Bulletin of Volcanology 2019, 81, 23 .
AMA StyleTeresa P. Silva, Daniel P. S. De Oliveira, João Pedro Veiga, Paula Ávila, Carla Candeias, Eduardo Salas Colera, Rita Caldeira. Mineralogy and chemistry of incrustations resulting from the 2014–2015 eruption of Fogo volcano, Cape Verde. Bulletin of Volcanology. 2019; 81 (4):23.
Chicago/Turabian StyleTeresa P. Silva; Daniel P. S. De Oliveira; João Pedro Veiga; Paula Ávila; Carla Candeias; Eduardo Salas Colera; Rita Caldeira. 2019. "Mineralogy and chemistry of incrustations resulting from the 2014–2015 eruption of Fogo volcano, Cape Verde." Bulletin of Volcanology 81, no. 4: 23.
Good conservation and restoration practices of cultural heritage assets rely on the knowledge of original materials. In the framework of the HERACLES Project (HERACLES—HEritage Resilience Against CLimate Events on Site, H2020 Grant Agreement 700395), dealing with the effects of climatic actions and natural hazards on built heritage, a set of important heritage sites are currently under study to improve their resilience against climate events. Among these are the medieval Gubbio Town Walls in Italy. The present work focuses on the mortars and binders of this monument and collected samples related to different parts of the Walls, corresponding to various historical periods of construction and interventions. They were characterized to determine their minerochemical composition, thermal behavior, and morphology. For that purpose, ex-situ laboratory techniques, such as X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), polarized light microscopy (PLM), scanning electron microscopy (SEM), and simultaneous differential thermal analysis and thermogravimetry (TG-DTA) were used to discern trends in different sampling areas due to construction/reconstruction periods and building techniques.
Fernanda Carvalho; Andreia Lopes; Antonella Curulli; Teresa Pereira Da Silva; Maria Margarida R. A. Lima; Giampiero Montesperelli; Sara Ronca; Giuseppina Padeletti; João Pedro Veiga. The Case Study of the Medieval Town Walls of Gubbio in Italy: First Results on the Characterization of Mortars and Binders. Heritage 2018, 1, 468 -478.
AMA StyleFernanda Carvalho, Andreia Lopes, Antonella Curulli, Teresa Pereira Da Silva, Maria Margarida R. A. Lima, Giampiero Montesperelli, Sara Ronca, Giuseppina Padeletti, João Pedro Veiga. The Case Study of the Medieval Town Walls of Gubbio in Italy: First Results on the Characterization of Mortars and Binders. Heritage. 2018; 1 (2):468-478.
Chicago/Turabian StyleFernanda Carvalho; Andreia Lopes; Antonella Curulli; Teresa Pereira Da Silva; Maria Margarida R. A. Lima; Giampiero Montesperelli; Sara Ronca; Giuseppina Padeletti; João Pedro Veiga. 2018. "The Case Study of the Medieval Town Walls of Gubbio in Italy: First Results on the Characterization of Mortars and Binders." Heritage 1, no. 2: 468-478.
Teresa P. Silva; Maria-Ondina Figueiredo; M. Alexandra Barreiros; M. Isabel Prudêncio. Diagnosis of pathologies in ancient (seventeenth-eighteenth centuries) decorative blue-and-white ceramic tiles: Green stains in the glazes of a panel depicting Lisbon prior to the 1755 earthquake. Studies in Conservation 2014, 59, 63 -68.
AMA StyleTeresa P. Silva, Maria-Ondina Figueiredo, M. Alexandra Barreiros, M. Isabel Prudêncio. Diagnosis of pathologies in ancient (seventeenth-eighteenth centuries) decorative blue-and-white ceramic tiles: Green stains in the glazes of a panel depicting Lisbon prior to the 1755 earthquake. Studies in Conservation. 2014; 59 (2):63-68.
Chicago/Turabian StyleTeresa P. Silva; Maria-Ondina Figueiredo; M. Alexandra Barreiros; M. Isabel Prudêncio. 2014. "Diagnosis of pathologies in ancient (seventeenth-eighteenth centuries) decorative blue-and-white ceramic tiles: Green stains in the glazes of a panel depicting Lisbon prior to the 1755 earthquake." Studies in Conservation 59, no. 2: 63-68.
Rhenium is a very scarce element, occurring in the Earth's crust mainly carried by molybdenite (MoS2). Due to a very low availability comparative to actual industrial demand, rhenium is nowadays one of the most expensive mineral commodities and an increased interest is focused on ex- ploring residues resulting from a long-term mining, particularly of sulphide ore deposits. It is therefore noteworthy to assign the presence of rhenium (in a concentration up to 3 ppm) in the waste materials from the old sulphur factory at the abandoned mine of Sao Domingos (Iberian Pyrite Belt, Southeast Portugal), exploited since the Roman occupation of Iberia. Aiming at a potential sustainable recovery of rhenium as a by-product, X-ray near-edge absorption spectroscopy (XANES) was applied to clarify the Re-binding and mode of occurrence by comparing Re L3-edge XANES spectra obtained from mine waste samples (previously fully characterized by X-ray laboratory techniques) with similar spectra collected from Re-rich molybdenites (Mo1-xRexS2) and from Re-O model compounds configuring various valences and coordination environments of rhenium ions. Obtained results are commented, ruling out a possible Re-S binding and rather conforming with the binding of rhenium to oxygen in the analysed mine waste materials.
Maria-Ondina Figueiredo; Teresa Pereira da Silva; João Pedro Veiga; Daniel de Oliveira; Maria Jo~Ao Batista. Towards the Recovery of By-Product Metals from Mine Wastes: An X-Ray Absorption Spectroscopy Study on the Binding State of Rhenium in Debris from a Centennial Iberian Pyrite Belt Mine. Journal of Minerals and Materials Characterization and Engineering 2014, 02, 135 -143.
AMA StyleMaria-Ondina Figueiredo, Teresa Pereira da Silva, João Pedro Veiga, Daniel de Oliveira, Maria Jo~Ao Batista. Towards the Recovery of By-Product Metals from Mine Wastes: An X-Ray Absorption Spectroscopy Study on the Binding State of Rhenium in Debris from a Centennial Iberian Pyrite Belt Mine. Journal of Minerals and Materials Characterization and Engineering. 2014; 02 (02):135-143.
Chicago/Turabian StyleMaria-Ondina Figueiredo; Teresa Pereira da Silva; João Pedro Veiga; Daniel de Oliveira; Maria Jo~Ao Batista. 2014. "Towards the Recovery of By-Product Metals from Mine Wastes: An X-Ray Absorption Spectroscopy Study on the Binding State of Rhenium in Debris from a Centennial Iberian Pyrite Belt Mine." Journal of Minerals and Materials Characterization and Engineering 02, no. 02: 135-143.
Teresa P. Silva; Maria Ondina Figueiredo; M. Isabel Prudêncio. Ascertaining the degradation state of ceramic tiles: A preliminary non-destructive step in view of conservation treatments. Applied Clay Science 2013, 82, 101 -105.
AMA StyleTeresa P. Silva, Maria Ondina Figueiredo, M. Isabel Prudêncio. Ascertaining the degradation state of ceramic tiles: A preliminary non-destructive step in view of conservation treatments. Applied Clay Science. 2013; 82 ():101-105.
Chicago/Turabian StyleTeresa P. Silva; Maria Ondina Figueiredo; M. Isabel Prudêncio. 2013. "Ascertaining the degradation state of ceramic tiles: A preliminary non-destructive step in view of conservation treatments." Applied Clay Science 82, no. : 101-105.
Decorated glazed ceramic tiles are used as an ornamental art, constituting an important cultural heritage whose preservation is mandatory. Environmental conditions are responsible for the degradation of exposed ancient tile panels originating various pathologies, related to the development of microorganisms. This is the case of a valuable 18th century blue-and-white Portuguese tile panel called “Cura do Cego,” belonging to the collection of the National Tile Museum (MNAz), where green stains are nowadays observable in the glaze. A prospective diagnosis of this green tarnishing was the aim of the present work. Small tile fragments were directly irradiated using nondestructive techniques: X-ray fluorescence spectrometry with a wavelength-dispersive system (WDXRF) for chemical characterization of the tile glaze and X-ray powder diffraction (XRD) to assess the phase constitution of both the glaze and the ceramic body. A destructive technique (scanning electron microscopy with energy-dispersive system (SEM/EDS)) was applied to tentatively infer the chemical changes induced in the glaze by the green staining and also to characterize the morphology of the microorganisms associated to this staining. The obtained results are reported and discussed, as a preliminary step for testing an innovative nondestructive decontamination technique applying gamma radiation, particularly suitable for overcoming such tile pathologies.
Teresa P. Silva; Maria-Ondina Figueiredo; Maria-Alexandra Barreiros; M. Isabel Prudêncio; Prudê Maria-Isabel Ncio. Decorative 18th Century Blue-and-White Portuguese Tile Panels: A Type-Case of Environmental Degradation. Journal of Materials 2013, 2013, 1 -6.
AMA StyleTeresa P. Silva, Maria-Ondina Figueiredo, Maria-Alexandra Barreiros, M. Isabel Prudêncio, Prudê, Maria-Isabel Ncio. Decorative 18th Century Blue-and-White Portuguese Tile Panels: A Type-Case of Environmental Degradation. Journal of Materials. 2013; 2013 (1):1-6.
Chicago/Turabian StyleTeresa P. Silva; Maria-Ondina Figueiredo; Maria-Alexandra Barreiros; M. Isabel Prudêncio; Prudê Maria-Isabel Ncio. 2013. "Decorative 18th Century Blue-and-White Portuguese Tile Panels: A Type-Case of Environmental Degradation." Journal of Materials 2013, no. 1: 1-6.
The chemical and physical properties of rhenium render it a highly demanded metal for advanced applications in important industrial fields. This very scarce element occurs mainly in ores of porphyry copper-molybdenum deposits associated with the mineral molybdenite, MoS2, but it has also been found in granite pegmatites and quartz veins as well as in volcanic gases. Molybdenite is a typical polytype mineral which crystal structure is based on the stacking of [S-Mo-S] with molybdenum in prismatic coordination by sulphide anions; however, it is not yet clearly established if rhenium ions replace Mo4+ cations in a disordered way or else, if such replacement gives rise to dispersed nanodomains of a rhenium-rich phase. As a contribution to clarify this question, an X-ray absorption spectroscopy (XANES) study using synchrotron radiation was performed at the Re L3-edge of rhenium-containing molybdenite samples. Obtained results are described and discussed supporting the generally accepted structural perspective that rhenium is mainly carried by molybdenite through the isomorphous replacement of Mo, rather than by the formation of dispersed Re-specific nanophase(s).
Teresa Pereira da Silva; Maria-Ondina Figueiredo; Daniel de Oliveira; João Pedro Veiga; Maria João Batista. Molybdenite as a Rhenium Carrier: First Results of a Spectroscopic Approach Using Synchrotron Radiation. Journal of Minerals and Materials Characterization and Engineering 2013, 01, 207 -211.
AMA StyleTeresa Pereira da Silva, Maria-Ondina Figueiredo, Daniel de Oliveira, João Pedro Veiga, Maria João Batista. Molybdenite as a Rhenium Carrier: First Results of a Spectroscopic Approach Using Synchrotron Radiation. Journal of Minerals and Materials Characterization and Engineering. 2013; 01 (05):207-211.
Chicago/Turabian StyleTeresa Pereira da Silva; Maria-Ondina Figueiredo; Daniel de Oliveira; João Pedro Veiga; Maria João Batista. 2013. "Molybdenite as a Rhenium Carrier: First Results of a Spectroscopic Approach Using Synchrotron Radiation." Journal of Minerals and Materials Characterization and Engineering 01, no. 05: 207-211.
Indium is a typical chalcophile element of the Earth’s crust, with a very low average content that seldom forms specific minerals, occurring mainly as dispersed in polymetallic sulphides. Indium recovery is based primarily on zinc extraction from sphalerite, the prototype of so-called tetrahedral sulphides, wherein metal ions fill half of the available tetrahedral sites within the cubic closest packing of sulphuranions, leaving interstices accessible for further in-filling. Ascertaining the tendency towards the establishment of In-In interactions through an x-ray absorption spectroscopy approach would efficiently contribute to understanding the behavior of indium in the carrier mineral. The successful results of applying such a near-edge absorption (XANES) study at In L3-edge to samples collected at the Lagoa Salgada polymetallic orebody in the Iberian Pyrite Belt (IPB) are described and the crystal chemistry of indium is re-evaluated, disclosing a potential clue for the metal binding state in polymetallic sulphides.
Maria-Ondina Figueiredo; Teresa Pereira Da Silva; Daniel De Oliveira; Diogo Rosa. Indium-Carrier Minerals in Polymetallic Sulphide Ore Deposits: A Crystal Chemical Insight into an Indium Binding State Supported by X-ray Absorption Spectroscopy Data. Minerals 2012, 2, 426 -434.
AMA StyleMaria-Ondina Figueiredo, Teresa Pereira Da Silva, Daniel De Oliveira, Diogo Rosa. Indium-Carrier Minerals in Polymetallic Sulphide Ore Deposits: A Crystal Chemical Insight into an Indium Binding State Supported by X-ray Absorption Spectroscopy Data. Minerals. 2012; 2 (4):426-434.
Chicago/Turabian StyleMaria-Ondina Figueiredo; Teresa Pereira Da Silva; Daniel De Oliveira; Diogo Rosa. 2012. "Indium-Carrier Minerals in Polymetallic Sulphide Ore Deposits: A Crystal Chemical Insight into an Indium Binding State Supported by X-ray Absorption Spectroscopy Data." Minerals 2, no. 4: 426-434.
Ferrihydrite is natural ferric oxyhydroxide occurring exclusively nanocrystalline. With ideal formula 5 Fe2 O3 . 9 H2 O, ferrihydrite is quite abundant in sediments, weathering crusts and mine wastes, being characteristic of red pre-soils formed by loose weathered rock plus mineral debris (regoliths) and commonly designated as “2-line” or “6-line” on the basis of the broadened maxima observed in the X-ray diffraction pattern. Synthetic nanocrystalline “6-line” ferrihydrite was recently studied through methods based on atomic-pair distribution functions disclosing the possible occurrence of icosahedral clusters formed by twelve octahedra centred by an inner tetrahedron, all filled by Fe 3+ ions. However, Mössbauer studies were inconclusive about the existence of 4-coordinated iron, thus suggesting that the tetrahedral cation may well be Si4+. In view of such structural uncertainty, a XANES study at the Fe K-edge was undertaken on ferrihydrite from a regolith to ascertain the occurrence of tetrahedral iron. Comparison with data collected from well crystallized iron oxide and hydroxide minerals where Fe 3+/2+ ions occur in octahedral and tetrahedral coordination is described and the results so far obtained are discussed, showing that supplementary study is needed on the elusive structure of ferrihydrite.
Maria Ondina Figueiredo; Teresa P. Silva; João Pedro Veiga. Natural Nanomaterials: Reappraising the Elusive Structure of the Nano-Sized Mineral Ferrihydrite through X-Ray Absorption Spectroscopy at the Iron K-Edge. Materials Science Forum 2012, 730-732, 931 -935.
AMA StyleMaria Ondina Figueiredo, Teresa P. Silva, João Pedro Veiga. Natural Nanomaterials: Reappraising the Elusive Structure of the Nano-Sized Mineral Ferrihydrite through X-Ray Absorption Spectroscopy at the Iron K-Edge. Materials Science Forum. 2012; 730-732 ():931-935.
Chicago/Turabian StyleMaria Ondina Figueiredo; Teresa P. Silva; João Pedro Veiga. 2012. "Natural Nanomaterials: Reappraising the Elusive Structure of the Nano-Sized Mineral Ferrihydrite through X-Ray Absorption Spectroscopy at the Iron K-Edge." Materials Science Forum 730-732, no. : 931-935.
The composition of cobalt blue pigments used in ancient blue-and-white Chinese glazes is known to have changed between the 14th and the 17th century and ratios of some main chemical components plus trace elements are relevant guide-lines to establish the porcelain manufacture period. Once archaeological findings of Chinese porcelains can contribute to set up dating processes, a study of blue-and-white porcelain shards recovered during recent excavations in Lisbon Old-City was carried out by non-destructive laboratory X-ray fluorescence spectrometry for chemical characterization, combined with X-ray absorption spectroscopy (XAS) using synchrotron radiation to ascertain the formal valence and coordination of pigmenting cobalt ions. Following a preliminary extended X-ray absorption fine-structure study that revealed a coordination of divalent cobalt ions slightly above four, a detailed analysis of the near-edge region of Co 1s X-ray absorption spectra (XANES) was carried out on the blue-and-white glazes from those archaeological Chinese porcelain fragments. Pre-edge features and edge details are discussed in comparison with XANES spectra obtained from model compounds with well known crystal structure – Co3O4, CoAl2O4 and Co2SiO4, plus a cobalt-based blue pigment (cerulean). Present chemical data validate the manufacture period of studied Chinese porcelains advanced by Art Historians on the single basis of stylistic features (late 16th and medium 17th century). Spectroscopic results confirm a coordination environment of pigmenting Co2+ ions close to tetrahedral and substantiate the dual role of cobalt as network former plus modifier in the glaze of ancient Chinese porcelains.
M.O. Figueiredo; T.P. Silva; J.P. Veiga. A XANES study of cobalt speciation state in blue-and-white glazes from 16th to 17th century Chinese porcelains. Journal of Electron Spectroscopy and Related Phenomena 2012, 185, 97 -102.
AMA StyleM.O. Figueiredo, T.P. Silva, J.P. Veiga. A XANES study of cobalt speciation state in blue-and-white glazes from 16th to 17th century Chinese porcelains. Journal of Electron Spectroscopy and Related Phenomena. 2012; 185 (3-4):97-102.
Chicago/Turabian StyleM.O. Figueiredo; T.P. Silva; J.P. Veiga. 2012. "A XANES study of cobalt speciation state in blue-and-white glazes from 16th to 17th century Chinese porcelains." Journal of Electron Spectroscopy and Related Phenomena 185, no. 3-4: 97-102.
D. P. S. De Oliveira; João Xavier Matos; Carlos Rosa; Diogo Rosa; Maria Ondina Figueiredo; T. P. Silva; F. Guimaraes; João Ricardo Silva Carvalho; A. M. M. Pinto; Jorge Relvas; F. K. M. Reiser. The Lagoa Salgada Orebody, Iberian Pyrite Belt, Portugal. Economic Geology 2011, 106, 1111 -1128.
AMA StyleD. P. S. De Oliveira, João Xavier Matos, Carlos Rosa, Diogo Rosa, Maria Ondina Figueiredo, T. P. Silva, F. Guimaraes, João Ricardo Silva Carvalho, A. M. M. Pinto, Jorge Relvas, F. K. M. Reiser. The Lagoa Salgada Orebody, Iberian Pyrite Belt, Portugal. Economic Geology. 2011; 106 (7):1111-1128.
Chicago/Turabian StyleD. P. S. De Oliveira; João Xavier Matos; Carlos Rosa; Diogo Rosa; Maria Ondina Figueiredo; T. P. Silva; F. Guimaraes; João Ricardo Silva Carvalho; A. M. M. Pinto; Jorge Relvas; F. K. M. Reiser. 2011. "The Lagoa Salgada Orebody, Iberian Pyrite Belt, Portugal." Economic Geology 106, no. 7: 1111-1128.
Maria Ondina Figueiredo; T.P. Silva; M.J. Batista; J. Leote; M.L. Ferreira; V. Limpo. Uranium in surface soils: An easy-and-quick assay combining X-ray diffraction and X-ray fluorescence qualitative data. Journal of Geochemical Exploration 2011, 109, 134 -138.
AMA StyleMaria Ondina Figueiredo, T.P. Silva, M.J. Batista, J. Leote, M.L. Ferreira, V. Limpo. Uranium in surface soils: An easy-and-quick assay combining X-ray diffraction and X-ray fluorescence qualitative data. Journal of Geochemical Exploration. 2011; 109 (1-3):134-138.
Chicago/Turabian StyleMaria Ondina Figueiredo; T.P. Silva; M.J. Batista; J. Leote; M.L. Ferreira; V. Limpo. 2011. "Uranium in surface soils: An easy-and-quick assay combining X-ray diffraction and X-ray fluorescence qualitative data." Journal of Geochemical Exploration 109, no. 1-3: 134-138.
Jarosite, KFe3(SO4)2(OH)6, is a secondary iron sulphate often found in acid mine drainage (AMD) environments, particularly in mining wastes from polymetallic sulphide ore deposits. Despite the negative environmental connotation usually ascribed to secondary sulphate minerals due to the release of hazardous elements to aquifers and soils, jarosite acts as an efficient remover and immobilizer of such metals, particularly lead. The mineral chemistry of jarosite is reviewed and the results of a Fe K-edge XANES (X-Ray Absorption Near-Edge Structure) study of K-, Na- and Pb-jarosite are described and discussed within the context of the abandoned old mines of São Domingos and Aljustrel located in southern Portugal, in the Iberian Pyrite Belt (IPB).
Maria-Ondina Figueiredo; Teresa Pereira Da Silva. The Positive Environmental Contribution of Jarosite by Retaining Lead in Acid Mine Drainage Areas. International Journal of Environmental Research and Public Health 2011, 8, 1575 -1582.
AMA StyleMaria-Ondina Figueiredo, Teresa Pereira Da Silva. The Positive Environmental Contribution of Jarosite by Retaining Lead in Acid Mine Drainage Areas. International Journal of Environmental Research and Public Health. 2011; 8 (5):1575-1582.
Chicago/Turabian StyleMaria-Ondina Figueiredo; Teresa Pereira Da Silva. 2011. "The Positive Environmental Contribution of Jarosite by Retaining Lead in Acid Mine Drainage Areas." International Journal of Environmental Research and Public Health 8, no. 5: 1575-1582.
Iron is a powerful chromophore element whose pigmenting properties were the first to be recognized among transition metals. The interest in blue iron minerals as pigments for painting was enhanced with the use of vivianite—a natural hydrated ferrous phosphate, Fe3(PO4)2⋅8H2O—which in medieval Europe became an alternative to the expensive lapis lazuli, (Na, Ca)4(AlSiO4)3(SO4, Cl, S), a member of the ultramarines whose appreciated blue tone is due to the presence of sulfur polyanions. Conversely, vivianite coloring is attributed to the intervalence charge transfer (IVCT) Fe2+–Fe3+ that in later decades was studied by optical techniques and Mössbauer spectroscopy. However, the aging of blue vivianite pigments in old paintings has become a serious concern for conservators, but the aging process still awaits a satisfactory explanation. As an input to this problem, an X-ray absorption near-edge structure (XANES) study at the Fe K-edge of vivianite with different colors and origins was undertaken at the European Synchrotron Radiation Facility using the instrumental facilities of beamline ID-21. The analysis of pre-edge features corroborates previous data on the origin of vivianite color and emphasizes the need for a precautious assessment of iron speciation on the exclusive basis of XANES data. Actual results are discussed and further work is outlined.
Maria Ondina Figueiredo; T. P. Silva; João Pedro Veiga. The blue of iron in mineral pigments: a Fe K-edge XANES study of vivianite. Applied Physics A 2010, 99, 357 -361.
AMA StyleMaria Ondina Figueiredo, T. P. Silva, João Pedro Veiga. The blue of iron in mineral pigments: a Fe K-edge XANES study of vivianite. Applied Physics A. 2010; 99 (2):357-361.
Chicago/Turabian StyleMaria Ondina Figueiredo; T. P. Silva; João Pedro Veiga. 2010. "The blue of iron in mineral pigments: a Fe K-edge XANES study of vivianite." Applied Physics A 99, no. 2: 357-361.
Maria Ondina Figueiredo; Teresa Ondinada Silva; Pereira. Effect of oxygen sharing on the white line of S K-edge XANES spectra of sulphate minerals. European Journal of Mineralogy 2009, 21, 79 -83.
AMA StyleMaria Ondina Figueiredo, Teresa Ondinada Silva, Pereira. Effect of oxygen sharing on the white line of S K-edge XANES spectra of sulphate minerals. European Journal of Mineralogy. 2009; 21 (1):79-83.
Chicago/Turabian StyleMaria Ondina Figueiredo; Teresa Ondinada Silva; Pereira. 2009. "Effect of oxygen sharing on the white line of S K-edge XANES spectra of sulphate minerals." European Journal of Mineralogy 21, no. 1: 79-83.
A review is presented on constructive techniques plus materials and the processes involved in degradation phenomena observed in two historical monuments: the Zambujeiro dolmen (Portugal) and the Roman Aqueduct of Carthage (Tunisia). Dolmens are particularly impressive megalithic constructions for the dimensions of granite blocks. At Zambujeiro, the upright stones have undergone a catastrophic evolution after the archaeological exploitation due to accelerated weathering through a process apparently distinct from natural granite decay in nearby outcrops. The biological attack of granite minerals by lichen exudates has emphasized the hazardous character of bromine and more has been learnt about construction techniques, namely, the insertion in the mound of an impermeable clay stratum that hinders water penetration into the dolmen chamber. The characterization of original Roman ashlar blocks, including masonry and the diagnosis of Byzantine and medieval reconstruction testimonies in the Aqueduct of Carthage were the object of a detailed study by X-ray diffraction and synchrotron radiation X-ray fluorescence. Traditional constructive techniques and local construction materials were studied and successive historical, modern and recent rehabilitations were reappraised.
M.O. Figueiredo; T.P. Silva; João Pedro Veiga. Analysis of degradation phenomena in ancient, traditional and improved building materials of historical monuments. Applied Physics A 2008, 92, 151 -154.
AMA StyleM.O. Figueiredo, T.P. Silva, João Pedro Veiga. Analysis of degradation phenomena in ancient, traditional and improved building materials of historical monuments. Applied Physics A. 2008; 92 (1):151-154.
Chicago/Turabian StyleM.O. Figueiredo; T.P. Silva; João Pedro Veiga. 2008. "Analysis of degradation phenomena in ancient, traditional and improved building materials of historical monuments." Applied Physics A 92, no. 1: 151-154.
The colours of natural and synthetic beryl (ideally Be3Al2Si6O18) have been attributed either tothe presence of chromophore ions partially replacing Al and/or Be (Cr3+, Fe2+/3+, Mn2+) or to the occurrence of colour centres related to the presence of multi-atomic groups. However, no full explanation has been proposed for the blue colour in natural beryl gemstones (aquamarine) despite it being well established that bluish-green synthetic aquamarines containing Fe turn blue when heated for 1 h at 400°C.A X-ray absorption near-edge spectroscopy (XANES) study at the Fe K-edge was performed on blue beryl crystals from Licungo pegmatite (Mozambique) to ascertain the speciation state of this colouring element, reported in blue sapphire (ideally Al2O3) as a mixture of Fe2+ and Fe3+ in octahedral coordination. The general trend of the spectra is the same when synchrotron radiation (SR) impinges along the c axis of the hexagonal crystal, as well as along the a axis with c vertical. Conversely, a shoulder in the absorption edge is noticed when the incident beam is perpendicular to c, with this axis horizontal in the polarization plane of the SR beam, a reverse in the relative intensities of the two post-edge features is simultaneously observed. Pre-edge features accounting for Fe speciation (valence plus coordination) are identical in all three situations. Considering previous approaches which account for polarization, an explanation is suggested for the special effects observed on the Fe K-edge XANES spectra of analysed blue beryl crystals. Ideas on the origin of the blue colour of this mineral are also presented.
Maria Ondina Figueiredo; T. Pereira Da Silva; João Pedro Veiga; Carlos Leal Gomes; V. De Andrade. The blue colouring of beryls from Licungo, Mozambique: an X-ray absorption spectroscopy study at the iron K-edge. Mineralogical Magazine 2008, 72, 175 -178.
AMA StyleMaria Ondina Figueiredo, T. Pereira Da Silva, João Pedro Veiga, Carlos Leal Gomes, V. De Andrade. The blue colouring of beryls from Licungo, Mozambique: an X-ray absorption spectroscopy study at the iron K-edge. Mineralogical Magazine. 2008; 72 (1):175-178.
Chicago/Turabian StyleMaria Ondina Figueiredo; T. Pereira Da Silva; João Pedro Veiga; Carlos Leal Gomes; V. De Andrade. 2008. "The blue colouring of beryls from Licungo, Mozambique: an X-ray absorption spectroscopy study at the iron K-edge." Mineralogical Magazine 72, no. 1: 175-178.
Aged lead-rich, tin-opacified glazes from polychrome tiles manufactured in the 16th–18th century were studied to ascertain the structural role of lead. Glaze fragments with white, blue, yellow, brown and green colouring were analysed using non-destructive X-ray techniques, both laboratorial – X-ray diffraction to identify crystalline components – and synchrotron-based. Elemental analyses by synchrotron radiation X-ray fluorescence were performed at the former LURE photon microprobe (line D15A at DCI, in Orsay). The instrumental set-up of beamline BM29 at the ESRF, in Grenoble, was applied to collect X-ray absorption spectra at the Pb L3-edge. Natural minerals and synthetics with known crystal structure were used as model oxy-compounds to configure different formal valences and coordinations of lead ions by oxygen anions, and to interpret the effects upon details of X-ray absorption near-edge spectroscopy (XANES) spectra. Experimental evidence supports the general conclusion that lead is hosted by the glassy matrix, irrespective of the glaze colour. Furthermore, it was concluded that lead ions assume coordinations higher than usual for silica glasses, acting as network modifiers in the silica-lime-alkali glasses of ancient tile glazes.
M.O. Figueiredo; T.P. Silva; João Pedro Veiga. A XANES study of the structural role of lead in glazes from decorated tiles, XVI to XVIII century manufacture. Applied Physics A 2006, 83, 209 -211.
AMA StyleM.O. Figueiredo, T.P. Silva, João Pedro Veiga. A XANES study of the structural role of lead in glazes from decorated tiles, XVI to XVIII century manufacture. Applied Physics A. 2006; 83 (2):209-211.
Chicago/Turabian StyleM.O. Figueiredo; T.P. Silva; João Pedro Veiga. 2006. "A XANES study of the structural role of lead in glazes from decorated tiles, XVI to XVIII century manufacture." Applied Physics A 83, no. 2: 209-211.