Browning Phenomenon of Medieval Stained Glass Windows

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The browning phenomenon of medieval stained glass windows Jessica Ferrand, Stephanie Rossano, Claudine Loisel, Nicolas Trcera, Eric D. Van Hullebusch, Faisl Bousta, and Isabelle Pallot-Frossard Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/ac504193z • Publication Date (Web): 17 Feb 2015 Downloaded from http://pubs.acs.org on February 18, 2015

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Analytical Chemistry

The browning phenomenon of medieval stained glass windows Jessica Ferrand,: Stéphanie Rossano,˚,: Claudine Loisel,; Nicolas Trcera,¶ Eric D. van Hullebusch,: Faisl Bousta,; and Isabelle Pallot-Frossard; Université Paris-Est, Laboratoire Géomatériaux et Environnement, (EA 4508),UPEM, 77454 Marne-la-Vallée, France, Laboratoire de Recherche des Monuments Historiques, 29 rue de Paris, 77420, Champs-sur-Marne, France, and SOLEIL Synchrotron, l’Orme des merisiers St Aubin BP48, 91192 Gif-Sur-Yvette Cedex, France E-mail: [email protected]

Abstract In this work, 3 pieces of historical on-site glass windows dated from the 13th to 16th century and one archaeological sample (8th century) showing Mn-rich brown spots at their surface or sub-surface have been characterized by optical microscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy. The oxidation state of Mn as well as the Mn environment in the alteration phase have been characterized by X-ray absorption spectroscopy at the Mn K-edge. Results show that the oxidation state of Mn and therefore the nature of the alteration phase varies according to the sample considered and is correlated with the extent of the brown alteration. The larger the brown areas the more oxidized the Mn. However, by contrast with literature, the samples presenting the more extended brown areas are not similar to pyrolusite and contain Mn mainly under a (+III) oxidation state. ˚

To whom correspondence should be addressed LGE ; LRMH ¶ SOLEIL :

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Introduction Manganese is a chemical element which has long been used as a colouring or a bleaching agent in glass production. 1,2 At high temperature (over 1400˝ C), Mn-bearing glasses are colourless and the most stable Mn oxidation state is Mn(II). 3 By contrast, glasses produced around 1200˝ C and containing Mn as unique colouring agent are purple due to the presence of Mn(III) ions 4 unless heated in a reduced atmosphere. 3 When combined with iron, manganese is used as a bleaching agent 5 - turning Fe(II) into Fe(III) - and glasses present a light-green colouration. Although manganese is a minor element in medieval glass composition in terms of concentration (0.3-2 wt% MnO), it is involved in the occurrence of a typical pathology of lime-potash glasses called "browning". 6,7 This phenomenon, that has been observed on on-site historical 8–13 and archaeological 6,14–19 samples of various localities and periods, leads to the formation of Mn-rich brown spots on or under the surface of the glass that darken the windows and hamper the artwork legibility. In order to recover the windows legibility, according to most curators’ will, and to develop effective treatments, investigations have been undertaken since the 1990’s to identify the causes leading to the browning appearance or to understand the effect of treatments. Experimental alterations have been conducted on model samples in order to evaluate the parameters responsible for the appearance of the browning zones. A Mn-free glass has thus been immersed in a Mn-rich solution leading to the formation of black areas 18 thus confirming the possibility of an external source of Mn in the browning process. Microbial effect has also been investigated. 20 In both cases, no identification of the phases obtained was conducted. Some studies have addressed the problem of the identification of the brown phase observed on archaeological samples. Square wave voltammetry has been used on archaeological samples and has concluded that the Mn-bearing phase was mainly under hydrated forms similar to γ -MnO2 or pyrolusite. 19 More recently, X-ray Absorption Spectroscopy (XAS) has been used on archaeological samples again 6,21 and the Mn-bearing phase has been proposed to be MnO2 (pyrolusite) in all studied samples on the basis of a fingerprint analysis. Recent work has considered the effect of chemicals on the Mn-rich phases observed on historical glasses in order to understand the fate of Mn after the treatments. 6 If the application 2 ACS Paragon Plus Environment

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of hydroxyl amine hydrochloride solutions appears to be efficient to reduce back the Mn, it has secondary effects such as leaching damage on the original remaining glass or provoke an expansion of the leached layer thus introducing mechanical damage. While a large variety of treatments (see 22,23 for a recent review by a stained glass windows restorer) have already been tested and used in order to reverse the browning process, no satisfactory treatment has yet been proposed. Moreover, the efficiency of the treatments appears to be dependent of the considered sample suggesting that the browning phenomenon might be more complex than initially thought. This work focuses on the identification of the Mn-bearing phases that produce the browning phenomenon on on-site stained glass windows. Due to the difficulty to access on-site glass windows and to limitations due to experimental constraints, the set of samples is restricted to three samples mainly dated from the 13t h to the 16t h centuries and originating from France. One archaeological sample (8t h century) has been added to the corpus for comparison. Optical microscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEMEDX) have been performed to characterize the samples and locate the Mn-rich zones. XAS and more precisely X-ray absorption Near Edge Structure (XANES) at the Mn K-edge has been used to provide information about (i) the oxidation state of manganese in the glass and in the brown area and (ii) the local environment around Mn in the Mn-rich phase and in the glass.

Experimental details Samples The corpus of samples (Table 1) consists of three historical samples (EV3, Luy and PLOG) and one archaeological sample (ROUEN). The three historical samples (Table 1) have been selected from a corpus of 24 historical samples 24 based on the occurrence of browning spots under visual inspection. Among this 24 samples, only 14 presented a Mn enrichment correlated with the browning. Due to experimental limitation only three samples presented Mn-rich spots of a size greater than 10 µ m2 thus allowing the use of XAS. EV3, that has been provided by the Vinum workshop, 3 ACS Paragon Plus Environment


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is of unknown locality. Its period of manufacturing (13t h century) has been evaluated by art historians and glassmakers on the basis of morphological observations (surface aspect, thickness,...). PLOG is a piece of stained glass window from St Thurien de Plogonnec (16t h century). PLOG has been provided by the Le bihan French workshop. Luy (16t h century) is a piece of stained glass window from St Julien church in Luyères. This sample was dismounted and brought to the Laboratoire de Recherches des Monuments Historiques (LRMH) to perform an identification of the pathology and to propose eventual methods of restoration and conservation. The ROUEN sample is a piece of stained glass window of the episcopal palace of Rouen. It has been discovered during an archaeological excavation in the north-west of France and dates from the end of the 8t h , beginning of the 9t h century. Luy and ROUEN samples are completely altered implying that no information could be obtained on their original colour or composition. EV3 and PLOG still present some unaltered parts. They are both uncoloured but painted glasses. The composition of EV3 and PLOG unaltered areas and of the altered areas of the four samples are given in table 1. To avoid misinterpretations, parts showing no trace of grisaille have been studied. In order to observe the glass windows sections, samples were embedded in resin, cut perpendicularly to the surface and polished. A set of crystalline compounds (Table 2) of abiotic or biotic origin and containing Mn under various oxidation states (II, III and IV) and/or environment (coordination states and neighbour nature) has been studied to help interpreting the XAS spectra of historical and archaeological samples.

SEM Scanning Electron Microscopy was performed on the sample sections. SEM pictures were obtained with a JEOL JSM 5600 LV scanning electron microscope. The electron beam was generated by a Tungsten filament with an accelerating voltage of 15 kV. The pictures were performed under low vacuum (0.17 mbar) in order to avoid sample coating and recorded in back scattered mode.


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Microprobe analysis The sample sections were carbon-coated to perform quantitative chemical analyses using the CAMECA SX 100 electron microprobe of the CAMPARIS analytical facility of the Pierre et Marie Curie University, Paris. The column conditions were set to 15 kV and 4 nA. The samples were analyzed for 5 sec/element in order to increase the probed volume and to minimize possible alkali evaporation. The unaltered parts of the samples appear to be homogeneous. Ten measurements have been averaged to derive the original glass composition (Table 1). Error bars are equal to ˘ the standard deviation calculated from the ten points of analysis. Four measurements were performed in the altered parts, but the results have not been averaged due to the heterogeneity of these areas. In table 1, only the most enriched manganese point is reported.

X-ray Absorption Spectroscopy XAS measurements at the Mn K-edge were performed on the LUCIA beamline 25 of the SOLEIL synchrotron facility with an injected electron energy and current of 2.75 GeV and 400 mA respectively. Elemental maps and XANES spectra of the stained glass windows have been measured using a Si(311) double-crystal monochromator in fluorescence detection mode using a 4-elements Si drift diode (SDD). For elemental map recording, a beam size of 4 x 4 µ m2 on the sample was achieved using dynamically bendable mirrors in Kirkpatrick-Baez configuration. X-Ray Fluorescence (XRF) element distribution maps were obtained using a photon energy of 7400 eV. The monochromator energy calibration was performed measuring the spectrum of a Fe foil at the Fe Kedge and setting the first inflection point to 7112 eV. To avoid photoreduction effects, XAS spectra were measured using a slightly defocused beam (9 x 9 µ m2 ). The beam was further attenuated by using a limiting slit of 50 µ m and three graphite foils of 500 µ m thickness. XAS spectra were collected with a step of 2 eV before the pre-edge region (6500-6530 eV), 0.1 eV in the pre-edge region (6530-6550 eV), 0.5 eV in the XANES region (6550-6580 eV) and 1 eV between 6580 and 6630 eV. To increase the signal to noise ratio, four spectra per sample were averaged together. Experimental spectra were normalized using the Athena software from IFEFFIT package. 26 Pre5 ACS Paragon Plus Environment


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edge features of glasses and altered phases have been fitted (not shown) using the fityk program. 27 One or Two pseudo-Voigt functions were necessary to model the pre-edge and one pseudo-Voigt function to model the contribution of the main edge to the pre-edge feature. All contributions were fitted simultaneously.

Results and discussion Sample characterization The three historical and the archaeological samples have been fully characterized using a combination of optical microscopy, SEM (Figure 1 and Figures S1-S3) and microprobe analysis (Table 1). Optical microscopy analyses allowed to locate the brown areas at the surface of the samples (Figures 1a and Figures S1a-S3a). The SEM-EDX analysis allowed to better image the sample (Figure 1b and Figures S1b-S3b). Finally microprobe analysis allowed to obtain quantitative chemical compositions of original glasses (when available) and a more precise estimation of the chemical composition of the altered zones (Table 1). The three historical samples show different alteration features. For the EV3 sample (Figure 1a), two zones (z1 and z2 ) can be distinguished besides unaltered glass (z3 area). The original glass is a lime potash glass containing 5.3 wt% K2 O and 20.4 wt % CaO (Table 1). The brown spot is located in the z1 area and has a size of 10x10 µ m2 . It is located in the surface and sub-surface of the glass windows in a region highly altered (z2 ) that show important loss in Ca, Na, Mg and K (Table 1). It is associated with a strong enrichment in MnO (0.6 wt% in unaltered glass but 10.5 wt% in the altered zone). Due to the small size of the Z1 brown area in EV3, the chemical analyses reported in table 1 as EV3al is centered on, but might not be strictly restricted to, the brown area. Only two zones can be distinguished in the Luy sample (Figure S1), as no more original glass is present. The brown spots are located in a white area that appears to be laminated but also cracked (Figure S1b) which was not the case for the EV3 z2 area (Figure 1b). The cracking is probably due to the small thickness of the sample (around 100 µ m). The brown area is more extended than in 6 ACS Paragon Plus Environment

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the EV3 case with a size of around 200x50 µ m2 . In the Luy sample, the brown area is very rich in manganese (10.3 wt% MnO) while the others elements have comparatively low concentrations (Table 1). Three zones can be distinguished in the PLOG microscopy images (Figures S2a-b). The original glass is a lime potash glass containing 10.6 wt % K2 O and 15.9 wt % CaO (Table 1). Similarly to Luy, the altered area (z2 ) is white but contains brown inclusions of dendritic shape. The brown area is much more extended than for the EV3 and Luy samples. Dendrites show typical sizes of around 10 µ m width for length that can reach 500 µ m or more. The brown area is again highly enriched in MnO (0.8 wt% in unaltered glass but 9.1 wt% in the altered zone) and the altered zone is depleted in Mg, Na, and K (Table 1). By contrast, the z2 area is much less depleted in Ca (13.3 wt %) as compared to the EV3 glass (1.4 wt %). The archaeological sample ROUEN (Figure S3) presents a high degree of alteration with brown areas greater than 500 µ m2 . No original glass can be evidenced and the sample is highly laminated and show some cracks. While the previous observations reveal clear differences in the facies and in the chemical composition of the altered zones, a better characterization of the Mn-bearing phase is needed to understand the browning phenomenon. Due to the small size of the Mn bearing phase, and to the eventual importance of the Mn oxidation state on the alteration process, µ -XAS has been used at the Mn K-edge for both its chemical selectivity and its spatial resolution.

X-ray absorption experiments : crystalline references To help distinguishing between the various oxidation states of Mn, a Si(311) monochromator has been chosen to enhance the energy resolution (on the LUCIA beamline, the energy resolution is 0.943 eV for Si(111) crystals and 0.197 eV for Si(311) crystals). Although Mn-bearing crystalline compounds have already been studied at the Mn K-edge using Si(111), 28–32 Si(220) 33–36 or even Si(511) monochromator crystals, 37 only few studies present measurements performed using a Si(311) monochromator. 38,39 A set of Mn-bearing crystalline compounds (Table 2) have thus been measured in order to ensure a pertinent comparison with our samples. The XANES spectra of crystalline compounds containing Mn in variable oxidation states and environment are reproduced 7 ACS Paragon Plus Environment


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on figure 2 for crystals characterized by a single Mn oxidation state and on figure 3 for multiple site and/or Mn oxidation state crystals. The spectra vary strongly from one compound to the other even for similar oxidation state and coordination number. Mn(II)-bearing compound spectra appear to be more featured than Mn(III) or Mn(IV) ones. The Mn(II) white line and pre-edge are located at lower energy than Mn(III) features again located at lower energy than Mn(IV) features in good agreement with results observed on other multivalent elements such as iron 40 or copper. 41 However, for similar oxidation state, the edge position can vary strongly hindering its use to evaluate the oxidation state of Mn. 34 By contrast, the shape of the pre-edge varies with the oxidation state of Mn only and might thus be used to qualitatively evaluate it. For the compounds presented in this work and containing a single oxidation state, the Mn(II) pre-edge is composed of a slightly asymmetric feature whose maximum is located between 6539.4 and 6540.4 eV depending on the compound considered. The Mn(III) pre-edge is composed of two features separated by around 2 eV. The low energy component is located at 6539.7 eV and is thus very close to the position of the Mn(II) pre-edge feature. The Mn(IV) pre-edge is composed of one feature that can be decomposed into three components. 34 The pre-edge maximum of the Mn(IV) feature is located around 6542.5 eV. For compounds containing several Mn oxidation states (Figure 3) the shape of the pre-edge is more complex due to the superimposition of the signals due to the different oxidation states. Intense pre-edges (jacobsite figure 2 ; braunite and hausmannite figure 3) are due to the occurrence of Mn in non-centrosymmetric sites. More details about the transitions responsible for the preedge features of Mn-bearing compounds and their intensities can be found in previous works using RIXS 42 or XAS. 34

X-ray absorption experiments : stained glass windows Chemical distribution maps have been measured for the four samples in order to locate the Mnrich zones at which XANES spectra should be measured (Figure 4 and Figures S4-S6). EV3 is the only sample whose distribution maps cover unaltered and altered areas (Figure 4). The elemental distribution maps of Si, K, Mn, and Fe in the glass region delimited by the white rectangle (Figure 8 ACS Paragon Plus Environment

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1b) are represented on figure 4. As Si is present in both unaltered and altered areas, the distribution of silicon allows to image the boundaries of the sample. The potassium distribution allows to distinguish the original glass (K-rich/red) from the altered area (K-depleted/green). The outer layer of the sample appears to be completely depleted in potassium. The Mn-rich spot is located in the K-depleted zone of the altered part of the sample close to the sample surface. No correlation has been observed between iron and manganese distribution. For the three other samples (Figures S4-S6), no original glass is observed in the range of the chemical maps. The concentrations in potassium are consequently very low. The Mn rich regions are more extended than in the case of the EV3 sample, signing a higher degree of alteration. Except in the case of the ROUEN sample (Figure S6), the hot spots in Mn do not coincide with Fe-rich areas. Luy and ROUEN do not present any remaining unaltered area. XANES spectra of unaltered glasses have been measured for EV3 and PLOG. As the two spectra appeared to be identical, only one XANES spectrum is presented on figure 5. As expected, the XANES of the original glass is not much structured. It is characterized by 5 features (Figure 5). The pre-edge (A) is located at 6539.8 eV. The B shoulder is located at 6546.8 eV and has already been observed in other medieval glasses. 43 The white line C is located at 6552.2 eV. Two other features are observed at 6569 eV (D) and 6606.4 eV (E). The pre-edge has been fitted using one pseudo-Voigt function located at 6539.8 eV typical of predominant Mn(II). This is in good agreement with the Mn speciation in glasses of variable composition but synthesized at high temperature (1400˝ C) 36,44,45 or in ancient glasses. 6,21,32,39,46 The XANES spectra of the Mn-bearing alteration phase are shown on figure 5 and compared with the XANES spectrum of the original glass previously described and with the XANES spectrum of the archaeological glass (ROUEN). These spectra have been difficult to acquire due to the high reactivity of the Mn-bearing phase under the beam (photoreduction). This effect was most probably enhanced by the microsize of the beam and the high flux of the SOLEIL synchrotron. In order to overcome this difficulty, the beam has been defocused (from 4x4 µ m2 to 9x9 µ m2 ) and filtered before it arrived on the sample. The low flux of photons achieved (0.044 1010 photon/mm2 /s



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instead of 2.2 1010 photon/mm2 /s with a defocused beam) explains the low signal to noise of the spectra. Similar technical difficulties have been encountered by previous authors 6 but defocusing of the beam was sufficient to avoid the photoreduction effect. In previous experiments conducted with Si(111) crystals by the present coworkers, photoreduction was probably instantaneous for any samples thus leading to the detection of a Mn(II)-bearing alteration phase whatever the sample considered. This might be explained by the enhance brightness of Si(111) crystal monochromator as compared to Si(311) one. Depending on the sample, the sensitivity of the Mn phase to the synchrotron beam appeared to be slightly different. Sensitivity was maximum for Luy, PLOG and ROUEN whereas graphite filters were not necessary to ensure the stability of the EV3 sample. This observation suggests that the alteration phases are different from one sample to the other. This result is confirmed by the analysis of the pre-edge and XANES regions. EV3 and Luy pre-edges have been fitted with one pseudo-Voigt function located at the same position than the pre-edge (A) of unaltered glass (6539.8 eV) but with smaller intensities and a larger full width at half maximum suggesting that part of the Mn might be under the Mn(III) oxidation state. This trend is also evidenced by a shift of the edge position towards higher energy (Figure 5). A slight shift is also observed between EV3 and Luy suggesting that Luy is slightly more oxidized than EV3. The pre-edge of PLOG has been fitted with two pseudo-Voigt functions located at 6540 (A) and 6542.2 (A’) eV. This pre-edge shape is typical of Mn(III). 34,36,42 The Rouen pre-edge is very similar to the Plog one and has been fitted with the same two components suggesting that in this archaeological sample, manganese is also under the Mn(III) form at the difference with previous studies 6,21 that have concluded that Mn was mainly under the oxidation state (IV) for a large set of buried samples. These results suggest that the oxidation state of Mn increases in the following order : unaltered glass < EV3 < Luy < PLOG going from a predominant Mn(II)-bearing compound to a predominant Mn(III)-bearing phase. Concomitantly to the modification of Mn oxidation state, the shape of the XANES spectra is modified signing a transformation of the Mn-bearing phase. While the XANES spectrum of EV3 is still close to the unaltered glass one, modifications already occurred. The B feature is no more


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evidenced and the maximum of the E feature has shifted towards lower energy. The spectrum of Luy is further modified with the decrease in intensity of the C feature and the appearance of a feature around 6560.5 eV. This last feature appears to be the maximum of the PLOG and the Rouen spectra suggesting that the altered phase of Luy might be an intermediate phase between EV3 and PLOG. This evolution of the alteration phase from EV3 to PLOG is an important result that has never been observed previously. Indeed, in already published work, 21 the Mn bearing phase was suggested to be identical among all the studied samples and mainly characterized by a Mn(IV) oxidation state even if a slight proportion of Mn(III) has not been excluded. In the present work, the evolution of the Mn-bearing phase seems to correlate with the extent of the brown areas. The larger the brown zones, the more oxidized the Mn. ROUEN and PLOG that present the more extended brown areas are characterized by a Mn(III) oxidation state. This suggests that all the samples studied in this work present alteration phases different from the one observed on the samples studied by Schalm and coworkers. 21 Whereas this conclusion might be relevant for the historical glass windows, it is questionable why the ROUEN alteration phase is not similar to the archaeological samples studied in the work of Schalm and coworkers 21 despite similar age. Although it cannot be excluded that geochemical conditions of alteration might be different, the XAS study of Schalm and coworkers suffers a lack of resolution. With a 1 eV step in the XANES region, the pre-edge analysis is not usable to accurately determine the Mn oxidation state as preedge features are hardly distinguishable on their spectra. A definite identification of the Mn-bearing phases would have necessitated the precise determination of the Mn environment. However, the low photon flux, due to the graphite filters and to the Si(311) monochromator did not allow to measure good EXAFS data. Previous works on archaeological samples have concluded, on the basis of XAS experiments, 6,21 ESR 14 or square voltammetry experiments, 19,47 that Mn was located in MnO2 (pyrolusite) or in a hydrated γ -MnO2 respectively. The data displayed in the present study disagree with those previously published. The pyrolusite spectrum (Figure 2) is indeed completely different from all the spectra measured for altered parts of the historical glasses but also of the archaeological sample Rouen (Figure 5). In



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the present work, the XANES spectrum of the most altered samples (PLOG and Rouen) are very similar to the XANES spectrum of purpurite (Figure 6), a Mn-bearing phosphate. This result is partly supported by the microprobe analysis of the altered zone of the PLOG sample (Table 1) that is enriched in P as compared to the original glass. However, in the case of the ROUEN sample, the absence of original glass does not allow to evidence a P enrichment between unaltered and altered parts of the sample. Although this comparison on the basis of a simple fingerprinting analysis and of microprobe analysis of probably highy hydrated phases has to be considered very carefully, the occurrence of a Mn-bearing phase containing Mn, Fe, O and P in the altered parts of the glasses is in good agreement with the literature. 17,19

Conclusion New insights on the browning phenomenon of medieval stained glass windows have been obtained in this study thus arising new questions. Using highly resolved X-ray absorption experiments it has been shown that the Mn-bearing phase seems to change with the extent of the brown areas. It is characterized by an oxidation state of manganese of either (II) or (III) or a mixture of these two valences. The most extended Mn-bearing phase could be a phosphate-bearing phase. Moreover, the variability of the Mn-bearing phase might be a clue to understand the variable efficiency of cleaning treatments.

Acknowledgement The authors thank Geneviève Orial and Marie-Hélène Chopinet for fruitful discussions. A special thank to Lola Sarrasin for her participation in this project. We have been very happy to share this time with you. SR and JF warmly thank the LUCIA team which is always there to find a solution when difficulties pile up. A special dedicace to Pierre Lagarde and Anne-Marie Flank. We will miss your kindness and your skills. Crystalline references have been kindly provided by J.-C. Boulliard (IMPMC), F. Farges (MNHN), and B. Lanson (ISTERRE). Part of this work has been


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funded by the French Ministery of Culture via PNRCC program 2011-00051 (EPHEB).

Supporting Information Available Figures for Luy, PLOG and ROUEN samples have not been included in the manuscript for clarity reasons. This information is available free of charge via the Internet at http://pubs.acs.org/.

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(23) de Bourleuf, E. V. Caractérisation du phénomène de brunissement sur les vitraux et Optimisation des méthodes de traitement. M.Sc. thesis, Université Paris I Panthéon Sorbonne, 2012. (24) Ferrand, J. Le phénomène de brunissement des vitraux médiévaux : critères d’identification et nature de la phase d’altération. Ph.D. thesis, Université Paris-Est, 2013. (25) Flank, A.-M.; Cauchon, G.; Lagarde, P.; Bac, S.; Janousch, M.; Wetter, R.; Dubuisson, J.-M.; Idir, M.; Langlois, F.; Moreno, T.; Vantelon, D. Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 2006, 246, 269–274. (26) Ravel, B.; Newville, M. Journal of Synchrotron Radiation 2005, 12, 537–541. (27) Wojdyr, M. Journal of Applied Crystallography 2010, 43. (28) McKeown, D. a.; Kot, W. K.; Gan, H.; Pegg, I. L. Journal of Non-Crystalline Solids 2003, 328, 71–89. (29) Itai, T.; Takahashi, Y.; Uruga, T.; Tanida, H.; Iida, A. Applied Geochemistry 2008, 23, 2667– 2675. (30) Saratovsky, I.; Gurr, S. J.; Hayward, M. a. Geochimica et Cosmochimica Acta 2009, 73, 3291–3300. (31) Feng, X. H.; Zhu, M.; Ginder-Vogel, M.; Ni, C.; Parikh, S. J.; Sparks, D. L. Geochimica et Cosmochimica Acta 2010, 74, 3232–3245. (32) Abuín, M.; Serrano, A.; Chaboy, J.; García, M. a.; Carmona, N. Journal of Analytical Atomic Spectrometry 2013, 28, 11181124. (33) Villalobos, M.; Toner, B.; Bargar, J.; Sposito, G. Geochimica et Cosmochimica Acta 2003, 67, 2649–2662. (34) Farges, F. Physical Review B 2005, 71, 155109. 15 ACS Paragon Plus Environment


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Figure 1: Optical microscopy image (a) and SEM image (b) of the EV3 sample. Z3 zone corresponds to the original unaltered glass. Z1 and Z2 are altered parts of the sample. Z1 is the brown area while Z2 is a region depleted in alkali and earth alkali. The white rectangle shows the area that has been mapped by X-ray fluorescence during XAS experiments. The circles labelled 1 and 2 locate the XANES measurements of the brown phase and of the original glass respectively.


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Figure 4: X-ray fluorescence maps for Si, K, Mn, and Fe in the region of a browning spot for the EV3 sample (see also figure 1). The Si distribution maps the boundaries of the sample. The K distribution map allows to determine the region of unaltered glass (red-orange zone) while the Mn distribution map help localizing the Mn-rich spot at which XANES spectrum has been measured (point 1). Fe distribution was measured to explore eventual correlations between Mn and Fe oxides. The XANES spectrum of unaltered glass has been measured at point 2.




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Table 1: Chemical compositions (in oxide wt%) of unaltered (EV3 and PLOG) and altered (EV3al and PLOGal ) parts of EV3 and PLOG samples. For Rouen and Luy, only the composition of the altered part have been obtained as no unaltered glass remains. The compositions of the unaltered parts have been averaged on 10 points. Error bars are equal to ˘ the standard deviations of the measurements. For altered parts, measurements have been performed on 4 points in the brown areas but only the most enriched manganese point is given. Sample EV3 EV3al Origin unknown th Century 13 SiO2 58.4˘0.4 39.5 Al2 O3 3.4˘0.1 4.1 P2 O5 3.1˘0.1 3.3 K2 O 5.3˘0.1 0.2 CaO 20.4˘0.4 1.4 MnO 0.6˘0.0 10.5 FeO 0.6˘0.1 2.6 Na2 O 2.2˘0.1 0.0 MgO 3.0˘0.1 0.1 Total 97.0˘0.9 61.7

Luyal Luyères 16th 46.5 4.1 2.6 1.1 5.6 10.3 0.7 0.0 0.2 71.1

PLOG PLOGal Plogonnec th 16 55.6˘0.5 44.6 1.3˘0.1 1.9 3.8˘0.1 7.3 10.6˘0.3 0.3 15.9˘0.2 13.3 0.8˘0.1 9.1 0.5˘0.1 0.7 3.2˘0.1 0.1 7.5˘0.1 0.7 99.2˘0.4 78.0

Rouenal Rouen 8th -9th 26.2 1.4 0.8 0.3 3.3 20.8 1.0 0.0 0.0 53.8

Table 2: Crystalline compounds containing manganese under various oxidation states in different environments. Name Rhodochrosite 48 Manganosite 49 Jacobsite 50 Bixbyite 51 Groutite 52 Manganite 53 Purpurite 54 Hollandite 49 Pyrolusite 49 Braunite 55 Hausmannite 56 Birnessite (biogenic) 57 Chalcophanite 49 Vernadite (IRB-20-1) 58

Formula MnCO3 MnO MnFe2 O4 Mn2 O3 MnO(OH) MnO(OH) MnPO4 BaMn8 O16 MnO2 2` Mn Mn3` 6 SiO2 Mn3 O4 (Na0.3 Ca0.1 K0.1 )Mn2 O4 1.5H2 O ZnMn3 O7 .3H2 O `{2` Mw (H2 O)x Mny O3y [Mn1´z O2 ]

Coordination number r6s Mn r6s Mn r6s Mn+r4s Mn 2xr6s Mn r6s Mn r6s Mn r6s Mn 2xr6s Mn r6s Mn r8s Mn+ 3xr6s Mn r4s Mn+r6s Mn r6s Mn r6s Mn r6s Mn


Oxidation state Mn(II) Mn(II) Mn(II) Mn(III) Mn(III) Mn(III) Mn(III) Mn(IV) Mn(IV) Mn(II/III) Mn(II/III) Mn(III/IV) Mn(III/IV) Mn(II/III/IV)



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