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In Roman wall paintings, blue and green colours are less commonly encountered than red and yellow and were more expensive. Despite this, Pliny and Vitruvius describe the more common compounds used for these pigments, translated today as azurite, lazurite, chrysocolla, indigo and Egyptian blue for blues and verdigris, malachite, celadonite, glauconite and chlorite for greens. A confusion in their nomenclature is often found in the most common blue pigment that is the first manufactured compound, Egyptian blue. For greens, celadonite and glauconite were usual and called generically ‘green earths’, but they prove to be difficult to characterize analytically. In this paper, we evaluate the Raman spectroscopic identification of the characteristic Roman blue and green pigments as used in wall paintings using two different laser wavelengths (green and near infrared) and clarify their nomenclature.

—Chromceladonite in chromitites of the Southern Sarany chromium deposit (the Urals) occurs in two mineral associations: as crusts of acicular grains on uvarovite crystals and in thin-scale aggregates together with quartz and chlorite in brecciated zones developed after chromitites. The chemical composition of chromceladonite (wt %) is K2O 9.4, MgO 6.8, Cr2O3 17.1, SiO2 51.7, Al2O3 8.5, CaO 0.1, FeO 0.2, H2O+ 5.7. The sum is 99.7. Empirical formula: K0.82(Cr0.93Mg0.70 ⋅ Al0.25Ti0.05Fe0.01)Σ1.94[(Si3.56Al0.44)Σ4.00(O9.39OH0.61)Σ10(OH)2. Parameters of an elementary sell: a = 5.271(5), b = 9.015(6), c = 10.171(7) A, β = 101.82(8)°, V = 475(1) A3. The formation temperature of celadonite is as high as 300°C. A source of potassium for chromceladonite can be both country black shales and phlogopite-bearing rocks of the Southern Sarany massif.

We acknowledge the use of the LMA-INA (Universidad de Zaragoza) for access to dual beam equipment and expertise, the technical and human support provided by CICT of Universidad de Jaén (UJA, MINECO, Junta de Andalucía, FEDER), and the use of the PANalytical X'Pert Pro diffractometer of the Departamento de Mineralogía y Petrología, Universidad de Granada, Spain. María del Mar Abad is especially recognized for helping with the HRTEM work. The access to the HAADF FEI TITAN G2 microscope and the Philips CM20 (STEM) microscope was facilitated by the Centro de Instrumentación Científica of the Universidad de Granada. Thanks are extended to Javier Cuadros and an anonymous reviewer for their critical reviews and very helpful comments and suggestions., Glauconite and celadonite coexist at the nanometre scale in Early Jurassic submarine volcanic rocks of the Betic Cordillera (southern Spain) as a result of microbial activity. Samples from the limit between the two micas, recognizable in scanning electron microscopy, have been extracted using the focussed ion beam technique and studied by high-resolution analytical electron microscopy. Both micas are present as randomly oriented differentiated small crystals in the boundary area. They define clearly distinct compositional fields with gaps affecting to Fe, Mg and K. At the lattice scale, celadonite shows a high degree of order, with homogeneous orientation of the visible lattice parameters being a difference from glauconite, formed by packets no more than 10-layers thick. Smectite layers were also detected alongside glauconite packets, in accordance with X-ray diffractograms which indicate that glauconite is a mica-smectite interstratification being more than 90 % mica layers. The compositional gap indicates that celadonite is not the endmember of the glauconitic series and the two micas represent two different structural tendencies of mica, with glauconite having more distorted octahedral sheets, indicated by systematically higher b parameters than celadonite., MCIU-AEIFEDER PGC2018-094573-B-I00 ,PID2019-104624RB-I00 and RTI2018-093419-B-I00, Junta de Andalucia RNM-325, RNM-200 and RNM-179, Gobierno de Aragon E18_17R, European Fund

International audience; This study presents an inventory of possible chemical reactions affecting, or having affected, the Venus surface. Fluid rock reactions are simulated using experiments under conditions close to the present surface. Slabs or powder of several natural and synthetic silicate material (crystalline fresh basalt, altered basalt, obsidian, pumice and basalt glass) were reacted at 475°C in CO 2-H 2 O-H 2 S-SO 2-CO gas mixture. Most of the runs were carried out at roughly 90 bars with a duration of one week, some experiments having longer (one month) or shorter (one day) durations. The role of H 2 O content was explored through a wide range of water pressure: from dry gas for the current Venus conditions up to 590 bars (86%H 2 O) for early Venus (or other early terrestrial planets). The gas phase was sampled before the completion of the runs for chemical analysis of major gas components (CO, H 2 S, SO 2) as well as trace elements possibly released by the rocks. The altered samples were examined by a suite of mineralogical and chemical techniques (scanning and transmission electron microscopy, X-ray diffraction and spectroscopy). In dry atmosphere, the redox potential of the gas was close to the Ni/NiO buffer (−21.3 to −27.3 log fO 2), thus close to the current Venus conditions. The sample alteration is tenuous and limited to surface oxidation of glasses and coating of olivine by iron oxides, as well as the general deposition of (Ca,Na)SO 4 at the sample surface. The oxidation of glass is reflected in the formation of magnesioferrite under the surface and is accompanied by the release of Ca, Mg and Na into the gas phase or mineralized as sulfate at the surface. In wet atmosphere, obsidian recrystallizes into a mixture of plagioclase and amphibole while basaltic glass produced non-expandable clays minerals: chlorite-type (2:1:1) at the surface and likely celadonite (2:1) below the surface. Olivine is preserved. Using obsidian (the most alterable material) as a proxy of aluminosilicates, we discuss the surface reactions operating under supercritical conditions, and we used a shrinking-core equation for modeling the long-term reactions. These parametric exploration offer new insights into processes having affected the surface of Venus and contribute to the discussion of open questions such as the fate of water or the lifetime of vitreous dust or fine grain material if present in the current or past Venusian environment. Longer duration experiments will provide more kinetic parameters that can be extrapolated to the geologic history of Venus.

The data are given on the structure, chemical composition, and content of microelements in the ferromanganese and siliceous crusts of Pervenets Rise (the Sea of Japan). The crusts resulted from the cementation of small fragments of green clays (celadonite) with hydroxides of manganese (todorokite and birnessite) or silica. Initial was the formation of celadonite deposited during the eruption of ore-bearing hydrothermal solutions in the volcano caldera or on its slopes.The features of the crust structure show that they were originated through the diffusive infiltration of gas-hydrothermal solutions along the fractures or weakened zones in volcanic rocks and subsequent cementation of the celadonite already formed occurrences with manganese or siliceous oxides. The manganese and siliceous mineralization is separated in time and often in space and demonstrate more local distribution.

Terra verde, or Green Earth, a naturally-occurring mineral and green pigment consisting of celadonite or glauconite, is one of the most commonly-used pigments in works of art and their conservation. Its widespread use is owed primarily to its insensitivity to light, its neutral pH, and its high stability in air and moisture – attributes that collectively make it virtually unreactive with other components in an artefact. Notwithstanding this, the use of terra verde in the conservation of objects of cultural heritage is hindered due to its minimal tinting strength and hiding power, which makes the pigment effectively transparent when applied on the canvas with the most common binding media. This gives rise to problems in retouching during the restoration process. We report a robust and reliable method to overcome the problem of transparency through the application of crystal engineering techniques on the pigment Verona Green Earth, or Verona Terra Verde (VTV). The purchased pigment was co-crystallised with a selection of different co-formers and analysis was carried out on both starting compound and product via IR and XRF spectroscopy, hot-stage microscopy and powder X-ray diffraction. The results of the experiments conducted show an increase in the pigment's opacity without affecting its colour intensity.

This paper provides information on the structure, chemical composition, and concentrations of microelements in ferromanganese crusts and siliceous crusts sampled on the Pervenets Rise, Sea of Japan. The crusts were formed by cementation of small fragments of green clays (celadonite) by manganese hydroxides (todorokite and birnessite) or by silica. The primary process involved the generation of celadonite, which was deposited as ore-bearing hydrothermal brine that was discharged in the caldera of the volcano or on its slopes. The crusts have a structure that indicates their formation during diffuse percolation of gas-charged hydrothermal brine along fissures or weakened zones in volcanic rocks and subsequent cementation of the resulting celadonite deposits with manganese or siliceous oxides. The manganese and the siliceous mineralization are separated over time, as well as, frequently, in space, and are more local.

The present study aims to examine and treat the flowers canvas painting at the Egyptian Agric-ultural Museum. It is divided into three parts: a) USBDM, SEM-EDX, XRD, GC and FTIR studies, which revealed that the object is suffering from deterioration forms, e.g. ruptures, dust, cracks, missing parts, brittleness, fragility, acidified canvas, and incompatible treatments. The coloring materials are: The green is celadonite (K(Ca, Mg, Fe2) (Fe3Al) [Si4O10](OH)2), the red is hematite (Fe2O3), the blue is lazurite (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2), the beige is hematite (Fe2O3) mixed with barite (BaSO4) and zincite (ZnO), and the gray is carbon black (C). Additionally the ground layer consists of hydrocerussite PbCO3.(OH)2, cerussite Pb3CO3 and zincite ZnO binded with animal glue. The oil media is the poppy seed oil. b) The experimental part showed that 7% Beva371 in toluene is more suitable than the fish glue for object consolidation. c) The applied part covered cleaning, consolidation, patching, lining, completing the missing parts in the painting and ground layers and varnishing.

Large amounts of stone wastes are accumulated alongside different exploiting mines of amethyst geodes in south Brazil, which are becoming an unsustainable environmental issue. For an adequate use of hydrothermal basalt in agriculture as soil remineralizer, it is fundamental to know the material's mineralogy and geochemical variability. This study aims to evaluate the mineralogical and geochemical variability of the basalt from five mines at two positions (near and far from the geodes) in different size fractions to discuss their potential use in agriculture. X-ray diffraction (XRD), X-ray fluorescence (XRF) and petrographic analyses of thin sections were used. Petrographic and mineralogical analyses showed similar compositions for the rocks, consisting of plagioclases, pyroxenes, and opaque minerals with apatite as an accessory mineral. The rock samples located near the amethyst geodes presented slightly higher clay mineral contents than the distant ones. The clay mineralogy was composed of smectite and celadonite. The subfractions preserved the characteristics of the original material. Small geochemical and mineralogical variations were observed in the hydrothermal basalts regardless of the positions and the fraction sizes studied. These characteristics confer this material a high potential for use in agriculture as a soil remineralizer. This approach contributes both to solving an environmental issue associated with geode exploitation and to create an alternative for soil fertilization.

Saint Demetrius of Stomion is a historical monastery placed in the geographical area of Larissa town, Greece, with a remarkable presence from its founding until nowadays. The monastery's present catholicon (main church) has been dated in the 16th century and its surviving wall paintings were constructed in 1758. In addition to the characterization of the materials applied, the purpose of this study is to determine the existence of a sole pictorial phase, that of the mid-18th century, or the occurrence of overpaintings. Additionally, the present study aims to begin the establishment of the documentation of materials and techniques of the late post-Byzantine iconographic guilds, which acted in Central and Northern Greece. The collected samples were analyzed by means of microscopic, spectroscopic and thermogravimetric methods. The use of fresco technique is implied by the major participation of calcium carbonate in all of the painting layers, its main contribution in the plaster layers and the microstratigraphic analysis of the samples' cross-sections, while the scarce and local presence of a proteinaceous material implies the limited use of egg-tempera technique for the highlights. The pigment analysis shows that mostly traditional pigments were used, including cinnabar, ferrous pigments (ochre, sienna, umber), minium, Naples yellow, massicot/litharge, green earth (celadonite), malachite, carbon and bone black, calcite, kaolinite and lead white. The absence of modern pigments, the consistency of all samples regarding microstratigraphy and applied materials, and the lack of the extensive use of an organic medium, strongly suggest the lack of overpaintings.

A range of phyllosilicate compositions have been detected spectroscopically on Mars, but the largest fraction by far corresponds to clay minerals rich in Fe and Mg. Given that most of our understanding of Martian clays comes from remote sensing data, it is critically important to explore the details of how compositional variation affects spectral features of phyllosilicates. The greatest efforts have focused so far on near-infrared (NIR) spectroscopy. Recently, ambiguities have been detected in the NIR spectra of 2:1 phyllosilicates with intermediate Fe Mg content that preclude mineral and chemical discrimination. Such ambiguities highlight the relevance of exploring the visible spectral range as a complementary tool to characterize Martian phyllosilicates precisely. This article reports the investigation of laboratory reflectance spectra (330–800 nm) from 34 Earth analogues of Martian phyllosilicates with a wide range of Mg Fe composition, including nontronite, celadonite and saponite end-members, as well as interstratified glauconite-nontronite, talc-nontronite, and talc-saponite. The spectra indicated the presence of Fe(III) by absorption modulations and a decrease in total reflectance, especially in samples with tetrahedral Fe(III). Absorption bands at 370 and 420 nm were diagnostic of octahedrically and tetrahedrally coordinated Fe(III), respectively. Band amplitudes in the second derivative of the Kubelka-Munk function correlated positively with Fe(III) content (R2 > 0.8). Standard color analyses of the visible reflectance spectra under the CIE illuminant D65 indicated that the CIELAB color parameter a*10 was positively correlated with tetrahedral Fe(III), b*10 was positively correlated with octahedral Fe(III), and L*10 was negatively correlated with Fe(III) in both structural sites. Because Fe(II) was in relatively low amount, it did not provide clear spectral evidence. Multiple regression models using the amplitude of the diagnostic absorption bands predicted well absolute Fe content in the phyllosilicates (R2 = 0.89) and the ratio Fe/(Fe + Mg + Al) (R2 = 0.84). CIELAB color parameters improved the prediction of total Fe (R2 = 0.92) and the ratio Fe/(Fe + Mg + Al) (R2 = 0.93). Application of these analyses to Martian data has challenges set by Fe oxide dust coating and spatial and spectral resolution. However, these results mark an avenue to develop testable tools using visible-wavelength spectral data from both satellite and lander probes to help establishing Fe content and mineral identification of Martian phyllosilicates.

In this paper, we characterized for the first time the painting materials in rock art panels of the Patagonian archaeological locality La Angostura using a methodological approach that combined micro-Raman spectroscopy, attenuated total reflection Fourier Transform infrared spectroscopy, and X-ray fluorescence spectroscopy. In this way, we obtained detailed information on the red, green, and black pigments as well as on accessory minerals present in the paints. Hematite was the chromophore in the red paintings while celadonite and glauconite were identified in the green motifs. A manganese oxide, presumably pyrolusite, was characterized as the black pigment. The pigment compositions were also compared to those of natural sediments collected along the valley of the Chubut River, but the components of the red and green sediment samples differed from those present in the rock art paints. In the red motifs of two of the rock art panels, a relevant finding was the presence of gypsum and anhydrite as a priming layer of the corrugated rock support onto which the red paints were applied. This revealed a different painting technique in comparison to that at the other analyzed panels of La Angostura where paints were applied as thin layers on a smooth surface of the rock support. As far as we know, this is the first report on the identification of gypsum and anhydrite as components of a preparation layer in Patagonian rock art. This result contributes to the open discussion on the origin and function of calcium sulfate in rock art.

International audience; The structural and thermal relaxation overprint associated with the Neogene Alboran rifting have obscured the early Alpine tectono‐metamorphic evolution of the Alboran Domain, representing the metamorphic core of the Betic–Rif orogen of the western Mediterranean region. This study focuses on the Beni Mzala unit, forming the lower and deeper structural level of the Alpine metamorphic nappe stack (Upper Sebtides) in the Moroccan Rif. Meso‐ and micro‐scale structural investigations are carried out on high‐P aluminum silicate (Ky‐bearing)‐quartz segregations that occur as boudins within the main retrogressive syn‐greenschist foliation (S2/D2) and assumed to preserve the early M1 HP metamorphism associated with the Alpine orogenic construction in the Alboran Domain. These boudins host an early crenulated high‐P foliation (S1, D1/M1) made of quartz–kyanite–white mica–rutile. A large spread in white mica composition is documented, with the highest Si content per formula unit (up to 3.18 apfu) preserved along the S1 foliation and the lower Si content observed in the white mica marking the S2 retrogressive foliation (D2/M2) and the rim of S1 mica. Microtextural evidence documents post‐tectonic andalusite growth and static recrystallization of the quartz microlithons. Inverse (Zr‐in‐Rt thermometry) and forward modelling thermobarometry are integrated with Ar–Ar white mica geochronology to define the peak and exhumation pressure–temperature–time (P–T–t) path of the Beni Mzala unit. Minimum thermo‐baric estimates for the M1 event are ~1.4 GPa and 600°C, corresponding to a metamorphic gradient of ~11°/km, consistent with subduction zone metamorphism. Exhumation is constrained by re‐equilibration of the white mica composition (from high to low celadonite) between c. 29 and 22 Ma, during a nearly isothermal retrogressive path, with final equilibration at high‐T/low‐P conditions within the andalusite stability field (~0.2–0.3 GPa and 500°C). A minimum late Oligocene age is proposed for the Alpine D1 tectono‐metamorphic stage in the Rif, suggesting as feasible the previously proposed Eocene timing for the subduction‐zone metamorphism of the Alboran Domain. Conclusive evidence is provided to link the early Miocene tectono‐metamorphic event to a late thermal perturbation that affected the Alboran Domain at shallow crustal conditions, post‐dating the almost complete exhumation of the deep roots of the Alpine belt in the western Mediterranean.

The Voltri Unit and adjacent Tertiary Piedmont Basin, Western Alps, preserve complementary bedrock and sedimentary archives of Alpine subduction and exhumation. Combined PT modeling and phengite Rb–Sr geochronology of bedrock and clast samples shows that Fe–Ti metagabbros and metasediments preserve a record of protracted high-pressure metamorphism, between ~ 50 and ~ 40 Ma. Bedrock and clast Fe–Ti metagabbros yield similar eclogite-facies peak conditions, between 23 and 25 kbar, 510–530 °C; phengite, zoned in celadonite content, with cores > 3.5 Si c.p.f.u. and rims 10 Myr until subduction ceased on arrival of the European continent into the orogenic wedge. As shear tractions on the plate interface are considered to exceed available buoyancy forces for exhumation, we suggest that syn-subduction exhumation occurred along the wedge-plate interface.

International audience; Hypothesis: The objective is to elucidate the multiscale dynamics of water within natural mixtures of minerals, green earth pigments that are mainly composed of phyllosilicates containing large amount of iron. In particular, the interaction of water with the different kinds of surfaces has to be probed. One issue is to examine the influence of surface type, basal or edge, on the dispersion quality.Experiment: The study was carried out using 1H variable field NMR relaxometry on various green earth pigment dispersions and concentrations. To analyse the data, a new analytical model was developed for natural phyllosilicates containing large amount of paramagnetic centres.Finding: The proposed theoretical framework is able to fit the experimental data for various samples using few parameters. It allows to determining water diffusion and residence times in complex phyllosilicate dispersions. Furthermore, it makes it possible to differentiate the contribution of the basal and edge surfaces and their respective surface area in interaction with water. Moreover, NMR relaxation profile reveals to be highly sensitive to the structural aspect of the phyllosilicates and to the accessibility of water to iron, hence allowing to discriminate clearly between two very similar phyllosilicates (glauconite and celadonite) that are difficult to distinguish by standard structural methods.

Phengite series is a dioctahedral solid solution between two end-members of muscovite [K1[Al2]VI[Al1,Si3]IVO10(OH)2] and celadonite [K1[(Fe3+,Al)1,(Mg,Fe2+)1]VI[Si4]IVO10(OH)2], which have a hetero-valent substitution of AlVIAlIV &harr, (Mg, Fe)VISiIV. In this study, we report a hydrothermal-originated authigenic Mg-phengite-series mineral, which occurred as polycrystalline aggregates (Type 1), pore-fillings (Type 2) and well-crystallized lath form (Type 3) from the Haengmae Formation, a dolomite&ndash, pebble-bearing fine sand-sized dolostone, in South Korea. Based on micro-textural observation, three types of Mg-phengite are associated with crystalline dolomite, and are followed by calcite precipitation as pore-filling, indicating that these should be formed by the influx of a Mg-rich hydrothermal fluid after the deposition of some clastic sediments and before calcite-filling. The structural formula based on O10(OH)2 shows that the number of Mg atoms per formula unit (apfu) of Mg-phengite ranges from 0.00 to 0.70 with no Fe, which is relatively high, compared with the previously reported metamorphic phengites. In REEs mineral chemistry, the Mg-phengites are characterized by the enrichment of REEs and by the particular enrichment of LREEs in the polycrystalline aggregates of Mg-phengite. It strongly suggests that the Mg-phengite should be formed by the infiltration of the highly evolved Mg- and REEs-enriched hydrothermal fluid into the clastic sedimentary rock (Haengmae Formation) as a strata-bound form, syngenetically or during early diagenesis.

The morphology, chemical, and mineralogical composition of subsurface filamentous fabrics (SFF) from the Deccan Volcanic Province (DVP) were investigated to determine the origin of these spectacular aggregates. SFF occur in a wide variety of morphologies ranging from pseudo-stalactites to irregular fabrics and are classified as SFFIr (irregular) or SFFMa (matted). The SFF samples exhibit a thread-like (or filament-like) center from which mineral precipitation starts to form the final macroscopic morphologies. Detailed investigations revealed organic material (fungal chitin) in the innermost filamentous core, which may have acted as an initial nucleus for the mineralization processes. The morphometric characteristics of certain filamentous fabrics are very similar to those of microbial filaments and the fabrics formed from them but are clearly distinct from similar types of non-biological precipitates (fibrous minerals, speleothems, and &ldquo, chemical gardens&rdquo, ). These features indicate that the filamentous cores might be products of microbial communities that were active in the basaltic cavities. The SFF cross-sections display similar concentric layers of the mineral succession and reach thicknesses of several centimeters with spectacular lengths up to 100 cm and constant diameters. The typical mineralization sequence points to temporal variation in the chemical composition of the mineralizing fluids from Fe(Mg)-rich (Fe-oxides/-hydroxides, Fe-rich sheet silicates such as celadonite and di-/tri-smectite) to Ca-dominated (Ca-rich zeolites) and finally pure SiO2 (opal-CT, chalcedony, and macro-crystalline quartz). Assuming biological activity at least during the early mineralization processes, circumneutral pH conditions and maximum temperatures of 100&ndash, 120 &deg, C were supposed. The formation of filamentous cores including Fe-bearing phyllosilicates probably occurred near the surface after cooling of the lava, where the elements necessary for mineral formation (i.e., Si, Mg, Al, Fe) were released during alteration of the volcanic host rocks by percolating fluids.

In 2012, the ruins of a temple of the old Russian period were found during archaeological research in the medieval historical territory of Smolensk. The archaeological complex consists of the ruins of an ancient temple, built in the middle of the XIIth century AD, and adjacent to it from the South-West of the territory, which housed the remains of the market XI-turn XIII-XIV centuries AD and necropolis XIII–XVI centuries AD. Chronologically diverse use of the investigated territory up to the XVIth century AD was determined by the nearby Church. Approximately 1000 fragments of wall paintings, 5 fragments window glass and 4 glazed floor tiles were found near the ruins of the Church building. For the first time fragments of wall paintings medieval of Old Russian temple were dated by the AMS radiocarbon dating and went through chemical-technological research (analysis of the plaster foundation, the definition of used pigments) by X-RAY diffractometry (XRD) and scanning electron microscopy (SEM/EDS). Optical microscopy also was used for visual observations of the samples of the wall painting. According to the results of the radiocarbon analysis, the fragments of the wall paintings were divided into two chronological groups. The earlier belongs to the last quarter of the XIIth–the first quarter of the XIIIth century AD. Samples of the wall paintings from the second group are dated back to the third quarter of the XIIIth century AD. A narrow range of Accelerator Mass Spectrometry (AMS) radiocarbon dating of fragments of the murals, obtained from carbonates due to the presence of high content of C14 isotope in carbon of the plaster, is simultaneous in age to the moment of creation of the plaster base. As a result of chemical and technological researches of the fragments of the wall paintings it was established that the plaster basis of the fragments of the wall painting consists of two layers. The plaster base contains organic binders. Chemical and technological analysis of pigments presents the following results: (1) the basis of the blue paint layer is ultramarine (mineral) and anatase (mineral); (2) the basis of the green paint layer is celadonite (mineral); (3) the basis of the brown paint layer is ochre (clay); (4) black particles in the colorful mixture of brown is an organic wood coal pigment.

The Pulo do Lobo domain is one of the units exposed within the orogenic suture zone between the Ossa-Morena and the South Portuguese zones in the SW Iberian Variscides. This metasedimentary unit has been classically interpreted as a Rheic subduction-related accretionary prism formed during pre-Carboniferous convergence and eventual collision between the South Portuguese Zone (part of Avalonia) and the Ossa-Morena Zone (peri-Gondwanan terrane). Discrete mafic intrusions also occur within the dominant Pulo do Lobo metapelites, related to an intra-orogenic Mississippian transtensional and magmatic event that had a significant thermal input. Three different approaches have been applied to the Devonian-Carboniferous phyllites and slates of the Pulo do Lobo domain in order to study their poorly known low-grade metamorphic evolution. X-ray diffraction (XRD) was used to identify the mineralogy and measure crystallographic parameters (illite "crystallinity" and K-white mica b-cell dimension). Compositional maps of selected samples were obtained from electron probe micro-analysis, which allowed for processing with XMapTools software, and chlorite semiempirical and thermodynamic geothermometry was performed. Thermometry based on Raman spectroscopy of carbonaceous material (RSCM) was used to obtain peak temperatures. The microstructural study shows the existence of two phyllosilicate growth events in the chlorite zone, the main one (M-1) related to the development of a Devonian foliation S-1 and a minor one (M-2) associated with a crenulation cleavage (S-2) developed in middle-upper Carboniferous times. M-1 entered well into epizone (greenschist facies) conditions. M-2 conditions were at lower temperature, reaching the anchizone-epizone boundary. These data accord well with the angular unconformity that separates the Devonian and Carboniferous formations of the Pulo do Lobo domain. The varied results obtained by the different approaches followed, combined with microstructural analysis, provide different snapshots of the metamorphic history. Thus, RSCM temperatures are higher in comparison with the other methods applied, which is interpreted to reflect a faster re-equilibration during the short-lived thermal Mississippian event. Regarding the metamorphic pressure, the data are very homogeneous: very low celadonite content (0 %-10 %) in muscovite (and low values of K-white mica b-cell dimension; 8.995 angstrom mean value), indicating a low pressure-temperature gradient, which is unexpected in a subduction-related accretionary prism., This research has been supported by the Spanish Ministry of Science and Innovation (grant no. CGL2011-24101), the Spanish Ministry of Economy and Competitiveness (grant nos. CGL2015-71692-P, CGL2016-75679-P), the Andalusian Government (grant nos. RNM-148, RNM-179), and the doctoral scholarship to Irene Perez-Caceres from the Spanish Ministry of Science and Innovation (grant no. BES-2012-055754). The Raman facility in Paris has been funded by the city of Paris (Emergence program).

The present work studies the tuffs associated with the volcanic area of the Paleogene Sheinovets caldera, located on the southeastern part of the Rhodope massif, in Bulgaria. Its purpose is to describe the mineralogical and geochemical composition of the zeolitized volcaniclastic deposits in the broader area of Petrota village, in the northwesternmost part of the Greek regional unit of Evros, in northeast Greece. The samples studied in this work were collected from seven (7) different locations, covering an area of almost 4 km in length and 2 km in width. Macroscopically, the samples display a greyish-green hue and they are widespread in the area of study. They often contain fragments of the crystalline metamorphic basement (mica-schists, phyllites, amphibolites, quartzites) and/or rhyolitic clasts. A rhyolitic outcrop of greyish-pink hue is observed in the Mavri Petra region, probably related to the Rupelian acid volcanism that occurred in the Sheinovets caldera. The mineralogy of the tuffs was studied under light polarizing microscope and using Scanning Electron Microscopy (SEM), and it was further confirmed by X-ray powder diffraction (XRPD) method. The initial matrix of the tuffs consisted predominantly of glass shards that are now partly or fully altered into zeolites and clay minerals, such as celadonite, displaying characteristic pseudomorphic structures. The dominant zeolite is clinoptilolite, while in some areas the presence of mordenite is also noticed. Feldspar phenocrysts are abundant, and they are represented by plagioclase and sanidine. Although quartz crystals can be observed under light-polarizing microscope solely in metamorphic fragments, the presence of silica polymorphs was also confirmed through SEM and XRPD analysis, with quartz and cristobalite prevailing. The mineralogical assemblage includes phenocrysts of biotite and in some cases amphiboles, while pyroxene, epidote, garnet, titanite, apatite, zircon, ilmenite, magnetite and rutile are additional minerals which have been identified locally in accessory quantities. Chemical analysis was carried out for major and trace elements, using the X-ray fluorescence (XRF) method and 4 Acid digestion ICP-MS analysis, respectively. The samples of Mavri Petra region, exhibit high concentrations in Cu, Pb, Mn, V, P and W. The analyzed concentrations of U in the area of Palaeokklisi are relatively high in comparison to the rest due to its proximity to a fault. Towards the northwestern study area, close to the Greek-Bulgarian border, the concentrations of Sr appear to be particularly high, probably because the area is closer to the volcanic centre.

Agate samples collected from the vicinity of Asni and Agouim (Western Atlas, Morocco) were investigated using microscopic observations supported by Raman micro-spectroscopy. The agates are marked by the presence of various microtextures typical of epithermal vein deposits, including jigsaw-puzzle, feathery, and lattice-bladed. The first two indicate that the formation of agates was likely marked by recrystallization of metastable silica phases (i.e., opaline silica or massive chalcedony). The presence of lattice-bladed (after barite and calcite) quartz may be, in turn, ascribed to the boiling-related conditions that could have triggered the formation of abundant copper and iron sulfides found within silica matrix. Additionally, the local occurrence of growth lines (so-called Bambauer quartz) and intergrowth of length-slow and length-fast chalcedony are linked to the variations of physico-chemical conditions during rock formation (alkaline-acidic). According to Raman spectroscopy, silica matrix of the agates is made of &alpha, quartz with a local admixture of moganite (from 0.0 up to 78 wt.%), but also contains numerous solid inclusions of hematite, celadonite, as well as poorly-organized carbonaceous material and rutile. These phases were likely emplaced during low-temperature hydrothermal activity of SiO2-bearing fluids that originated from post-magmatic hydrothermal activity developed within host rocks and/or meteoric waters.

In porous media, effects of internal gradient caused by magnetic susceptibility contrast between the matrix and infilling fluid shifts transverse relaxation time (T2) to shorter time, resulting in imprecise classification of pore sizes. In shale, details of the effects of paramagnetic and clay minerals that induce the internal gradients are poorly understood. We measured a brine mixture with a granular form of minerals, including kaolinite, montmorillonite, glauconite, illite, pyrite, celadonite, and chamosite, to infer contributions of each to T2 relaxation in shale. Nuclear magnetic resonance (NMR) response of these samples was used to calculate the total mean logarithm of T2 (T2ML) and volume of water in the samples. Additionally, physical properties such as magnetic susceptibility, specific surface area, and elemental composition were acquired. Pore geometry, magnitude of internal gradients, pore-size distributions, and secular regimes in which the media relaxed (based on their shortest characteristic time scales) were characterized from these properties. These time scales measure the behavior of the relaxation regimes such as longitudinal relaxation time-to-T2 ratio and dependence of relaxation rate on echo spacing (tE). Glauconite illite, pyrite, chamosite, and kaolinite grouped into a small-pore system, whereas montmorillonite and celadonite grouped into large-pore systems. A free diffusion regime governed secular relaxation for kaolinite; a motional-averaging regime governed montmorillonite, celadonite, and large tE chamosite; whereas a localization regime dominated the rest of the minerals. We conclude that understanding the effects of internal gradients in shale is important to quantify the shortening of T2ML, which leads to overestimation of bulk fluid volume and, thus, underestimating NMR permeability when used as an input into permeability estimator equations.

Boles are markers of hiatus in successive eruptions of the Deccan flood volcanism (DFV) emplaced at the Cretaceous-Paleogene boundary that are interpreted to retain paleoenvironmental information from their subaerial exposure. To evaluate paleoenvironment during these hiatuses, mineralogy and geochemistry of three different colors of boles, i.e., red (dark = 10R-3/6 and light = 10R-4/8), brown (5YR-4/4) and green (5G-6/2) were examined. The plagioclase index of alteration (PIA) (loss of Ca and Na relative to Al) was between 76 and 81 for all the boles, indicating moderate chemical weathering that is probably due to their short subaerial exposures. Mass balance calculations show significant enrichments of K, Si, Mg and Rb in green and brown boles suggesting an allochthonous input that is interpreted as volcanic ash fallout. Mineralogically, the red bole is dominated by montmorillonite and hematite, the brown bole of ferruginous smectite and montmorillonite, and the green bole of celadonite and nontronite. Montmorillonite and hematite genesis in red boles indicates leaching in an oxidative environment at near neutral pH (~5.5 to 8) conditions. Further, heating of the altered basalt from emplacement of upper lava flows under subaerial-dry conditions could have also promoted the formation of hematite in red boles. The hydrothermal alteration of K and Mg enriched volcanic ash admixed with the altered lower flow basalt under slightly reducing oxidation potential led to the genesis of nontronite and celadonite in the green bole. The aluminous Fe-smectite in brown bole occurred from hydrothermal alteration of aluminous clays (e.g., montmorillonite). The different colored boles, therefore, suggest a range of weathering processes including chemical leaching to hydrothermal alteration in oxidative to reducing environmental conditions throughout DFV emplacement that could reflect changing surficial conditions associated with volcanically forced changes to the environment.

Agates from Ploczki Gorne hosted by Permian basaltic rocks are predominantly made of length-fast chalcedony, and subordinately megaquartz and quartzine. Moganite occurs in traces mainly in transparent, outer, darker regions of white-grey coloured agates. Silica matrix of agates comprises a wide variety of solid inclusions represented by celadonite, plagioclases, hematite, goethite, barite, calcite, heulandite-clinoptyloite, nontronite-saponite, and Mn-dioxides (ramsdellite). Mineral phases are locally accompanied by black aggregations of carbonaceous matter, which gives a Raman signature of disordered carbon. These organic components were probably deposited from a hydrothermal fluids at low-temperature conditions and originated from sedimentary rocks found in the surrounding area of Ploczki Gorne. The abundance of various SiO2 phases, mineral inclusions as well as various micro-textures (colloform, comb, feathery, and jigsaw-puzzle) in agates resulted from physicochemical fluctuations of SiO2-bearing mineralizing solutions at various stages of these gems formation. Agates from Ploczki Gorne formed during post-magmatic stage of basaltic host rocks evolution. Not only were the hydrothermal fluids enriched in silica, but also they contained other elements such as Na, Ca, Al, Mg, Mn, Fe, Ba, SO4, and CO2, which were mobilized from host rocks or surrounding area.

The synthesis of NH4-bearing muscovite at P = 6.3 GPa and T = 1000°C in equilibrium with NH3–H2O fluid is performed. It is determined that the newly formed muscovite is enriched in celadonite minal and contains ~370 ppm of NH4. The obtained data make it possible to conclude that ammonium-bearing micas have sufficient thermal stability and can transport crustal nitrogen to the mantle in the presence of a reduced water–ammonia fluid at fO2 less than the values of IW + 2 log units even in the regime of “hot” subduction. The key parameter that determines the efficiency of this mechanism for the deep nitrogen cycle is redox stability of NH4-bearing muscovite at the mantle PT–parameters.

In this study, material characteristics of wall paintings executed in 11th Century Byzantine Church located in archaeological site of Anaia (Turkey) were investigated to provide historical information of the painting techniques. For this purpose, physical, chemical and mineralogical compositions of the paintings were determined by X-Ray Diffraction, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy coupled with Energy Dispersive spectroscopy and Thermo-Gravimetric Analysis. Analysis results indicated that the paintings were executed using lime-secco technique. In this technique, pigments were mixed with lime and applied on a smooth plaster layer. Pigments used were mainly iron oxides for red, yellow and purple paintings, aluminosilicates such as celadonite for green paintings and lazurite for dark blue paintings.

Hydrothermally affected basaltic flows and volcaniclastic rocks in northwestern Parana (Brazil) display textural features associated with secondary minerals, reflecting the temperature intensity and evolution of the hydrothermal process. Determination of the secondary mineralogy and the geochemical processes associated with their precipitation are addressed in this paper. The lithotypes that comprise the bulk of the Parana Igneous Province have millimetric to centimetric vesicles filled by secondary minerals. Field data, petrographic descriptions, mineral characterization and mineral chemistry were used to analyze these secondary mineral phases. Matrix material in volcaniclastic rocks (e.g. shards, glass pisolites) precedes the precipitation of the secondary minerals. Coalescence and necking features are common in vesicles located on top of basaltic flows. Clay minerals identified as vesicle and/or fracture infillings include celadonite, illite/smectite (I/S) interestratifications, as well as montmorillonite and nontronite, with morphologies typical of authigenic volcanic processes such as cauliflower-like and honeycomb. The occurrence of different zeolites species is primarily controlled by CaO and Na2O activity in the hydrothermal fluid. Heulandite is the most pervasive zeolite, followed by stilbite and analcime. Calcite occurs in the center of vesicles, as the last crystallizing phase, or isolated in monomineralic vesicles. Vesicle formation occurred by magma degassing processes at temperatures of up to 1150 °C. However, infilling of these voids occurred later with the percolation of hydrothermal fluids external to the system. Although random from a geographical perspective, gradual decrease in temperature and fluid evolution were responsible for the systematic change in the mineral phases within individual vesicles. The hydrothermal fluid was marked by a Ca–Na signature, high cation/hydrogen ratio and low to intermediate temperatures, ranging between 50 and 200 °C. The controls for precipitation were mainly temperature and the chemical composition of the fluid, with high alkalinity and low H+ activity.

The aqueous chemistry, isotopic composition (δ18O and δ2H), and geothermometry of the Breitenbush Hot Springs area in the central Oregon Cascades were examined. Water samples were collected from springs (5), wells (8), and the Breitenbush River (2). Geothermometry was interpreted using the Reservoir Temperature Estimator (RTEst) software package and constrained by the reported mineralogy. Reservoir temperature was calculated assuming equilibration with chalcedony, celadonite, laumontite, heulandite, and epidote. Because of its relatively rapid reaction rate, calcite was presumed to remain equilibrated during cooling of the ascending reservoir waters. CO2(g) degassing from the springs was accounted for by adjusting the carbon content and temperature to be consistent with a cooling curve passing through the chemical composition of the deep well waters. The average estimated reservoir temperature of 137.1 ± 2 . 0 ∘ C is lower than the 174 to 180 °C reported in other multicomponent geothermometric studies. However, our new estimate is consistent with mineralogical, aqueous geochemical, and fluid inclusion data, and with geothermal borehole temperature measurements near the site. Stable oxygen and hydrogen isotope data indicate that the thermal waters at Breitenbush and Austin Hot Springs are a mixture of 4 to 8% "andesitic water" (Giggenbach, 1992) and local meteoric waters recharged at elevations of 1750 to 2200 m, along the crest of the Cascade Mountains. Br/Cl ratios, δ18O, and δD, and their correlation with Cl− concentrations from our study combined with data and analyses from other sources, suggests that Cl−, other halogens, and CO2 in the Breitenbush hot springs are primarily derived from degassing fluids rising from the serpentinized forearc mantle. The calculated reservoir temperature and average measured thermal water Cl− concentration were used with previously reported chloride-flux-based measurements by the USGS to estimate a hydrothermal discharge of 13.7 ± 1.6 L/s and an advective heat discharge of 7.1 ± 0.8 MW. This calculated hydrothermal heat loss is slightly less than Ingebritsen et al.'s (1992) previous estimate of 9 MW. However, it still represents a substantial transfer of heat from a relatively small, constant groundwater discharge.

X-ray Powder Diffraction (XRPD) is one of the non-destructive techniques habitually used for the structural analysis of crystalline solids. This technique can therefore be used to differentiate between crystalline and vitreous or amorphous solids such as Smalt Cobalt Blue or the binders used in paints. The “final” pigments used in the artist's palette are frequently composed of a complex mixture of inorganic and organic compounds, causing different interferences and matrix effects, such as filtering and signal overlapping and background noise increase. These effects can make difficult pigment identification and quantification contributing to mischaracterization. Nevertheless, when the experimental difficulties can be overcome, the results obtained are precise, definitive and useful. In the present research, the limitations were avoided or minimized by using an algorithm for data analysis like the one used by the XPowder™ software. In addition, most of the natural pigments used in the painting The Little Madonna of Foligno are identified and quantified. The preparation layers are composed of white lead, along with a homogeneous mix of several arsenic sulfides and small amounts of roselite. The color layer contains lapis lazuli and minor azurite for the blue colors, and cinnabar for the red ones. Other pigments found were: lead‑tin yellow, iron(III) oxy-hydroxides (red and yellow ochers), celadonite (green earth), and possibly olivine, diopside and other ferromagnesian minerals in the form of pyroxenes and amphiboles, whose diffraction lines also appear in the diffractograms, although with weak intensities and precise quantifications are not allowed. Crystalline Thenard's blue was not found.

Iron-bearing K-dioctahedral 1 M and 1 M d micas are abundant in diverse geological environments and vary in composition from illite to celadonite through Fe-illite, Al-glauconite, and glauconite. The chemistry and structural features of these micas are complex and heterogeneous, reliable diagnostic criteria are lacking, and the conventional mineralogical nomenclature is ambiguous, which complicate the identification of these mica varieties. The objectives of the present study were to reveal the structural and crystal-chemical variability in Fe-bearing, K-dioctahedral 1 M micas and to define composition ranges and identification criteria for the mica varieties in the series. A collection of samples of various compositions was studied using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. Analysis of the relationships between unit-cell parameters and cation composition showed that the series included four groups, namely, Fe-bearing illites, Al-glauconites, glauconites, and celadonites and each group was characterized by a specific combination of unit-cell parameters and variation ranges. The illite group contained two distinct subgroups; Fe-bearing, Mg-rich illites and Fe-illites; which differ in the range of cation compositions and in FTIR characteristics. The boundary between Fe-illites and Al-glauconites occurs at a unit cell b value of ~9.05 A and at ratios of octahedral Al to total trivalent octahedral cations that range between 0.60 and 0.65. The partially overlapping cation composition and cell parameter ranges may complicate the distinction between Al-glauconites and glauconites, which can still be unambiguously differentiated using FTIR data. The dramatically different XRD and FTIR characteristics confirmed that glauconite and celadonite should be treated as separate mineral species. The distinctive features of celadonite are relatively low c sinβ values and reduced | c cosβ /a | values combined with b parameters lower than glauconites, but similar to Fe-illites. Celadonites also have distinct and sharp FTIR absorption bands at specific positions in the Si-O and OH stretching regions.

Changes in the global Li-cycle, as recorded in the Li concentration and/or isotopic composition of seawater, have the potential to provide important insight into the controls on the long-term C-cycle. Understanding the magnitude and isotopic composition of the fluxes of Li into and out-of the ocean, and the controls on any variability in these, is necessary if we are to correctly interpret the paleo-record of the Li-cycle. Here the low-temperature (off-axis) hydrothermal sink is investigated using the volcanic section of the exceptionally preserved Troodos ophiolite. Using glass to define the protolith Li content, the uptake flux of Li is determined using bulk-rock analyses from four hydrologically distinct sections through the lava pile of the ophiolite. Differences in paleo-hydrological conditions in the crust appear to have played a significant role in controlling the uptake flux of Li with an ‘average’ uptake flux of equivalent to 14–21 × 10 9 mol yr −1 – this is considerably larger than generally assumed. Bulk-rock samples that contain a large seawater Li component have δ 7 Li of ∼10 ± 2‰. Celadonite separates have a δ 7 Li of ∼6 ± 1‰, considerably lighter than bulk-rock samples with the same Li content. Because celadonite is a significant repository for Li within the Troodos upper crust this means that another phase(s) must have markedly heavier δ 7 Li than the average bulk-rock; i.e. changes in the average mineralogy of altered crust will lead to changes in the bulk isotopic fractionation between the Li added to the upper oceanic crust and seawater (Δ SW-lava ). The shallowest samples in three of the four studied sections are isotopically lighter than deeper samples (but do not contain significant celadonite), again indicating that variations in alteration conditions and/or mineralogy can lead to variations in Δ SW-lava . Comparison with other studies of altered upper oceanic crust suggests that changes in alteration conditions lead to significant changes in Δ SW-lava . These changes likely reflect both a temperature dependence of the isotopic fractionation factor and a change in the fractionation factor due to changing mineral assemblage and/or mineral compositions and abundances. A significant portion of the increase in δ 7 Li of seawater over the past 50 Myr may be due to an increase in the bulk fractionation factor between seawater and Li added to the upper oceanic crust due to cooling bottom water.

The Late Triassic-Early Jurassic volcanic sequence of the Central Atlantic Magmatic Province (CAMP) of Morocco is classically subdivided into four stratigraphic units: the Lower, Middle, Upper and Recurrent Formations separated by intercalated sediments deposited during short hiatuses in volcanic activity. Although corresponding to a Large Igneous Province formed in continental environment, it contains subaqueous lava flows, including dominant pillowed flows but also occasional sheet flows. We present a study of the morphology, structure and morphometry of subaqueous lava flows from three sections located at the Marrakech High-Atlas (regions of Ait-Ourir, Jbel Imzar and Oued Lhar-Herissane), as well as an analysis of the sediments, in order to characterize them and to understand their environmental meaning. The analysis of clays by the diffraction method X-ray revealed the presence of illite, mica, phengite, celadonite, talc and small amounts of quartz, hematite, calcite and feldspar, as well as two pairs of interbedded irregular (chlorite Smectite/chlorite-Mica). Fibrous minerals such as sepiolite and palygorskite were not detected. The peperite of Herissane region (Central High Atlas) provided an excellent overview on the factors favoring the magma-sediment interaction. These are the products of a mixture of unconsolidated or poorly consolidated sediments, low permeability with a low viscosity magma. The attempt of dating palynology proved unfortunately without results.

To fully understand phyllosilicates on Mars, it is beneficial to study analog deposits on Earth. One attractive candidate for martian phyllosilicates is the intrabasaltic bole beds (palaeosols) from the Deccan Volcanic Province of India. Eleven samples from the upper-layer red Deccan bole beds and underlying yellow and green Deccan bole beds were analyzed by X-ray diffraction (XRD), near-infrared (1.0–2.5 µm) and mid-infrared (5–15 µm) reflectance spectroscopy. Analysis of the bole beds indicated that the red boles are composed of a mixture of montmorillonite and hematite, yellow boles contain vermiculite and minor montmorillonite and green boles are composed mainly of nontronite (smectite) and celadonite (mica). While the bole beds are all chemically similar to each other and to the underlying basalt from which they were weathered, they are mineralogically different. This suggests transformation from one mineral to the next without ion transfer or loss which could be indicative of a limited-water environment. In fact, celadonite can transform into smectites (such as montmorillonite), often with vermiculite as an intermediate step. This not only explains the stratigraphy and mineralogy of the Deccan bole beds but may also explain the layered phyllosilicates identified in various, global locations on Mars. The transition observed in the Deccan bole beds suggests an evolution of the alteration process from deuteric alteration to low-temperature weathering, likely due to changes in temperature, in a closed system (no significant ion transfer) as evidenced by the minerals’ similar chemistry. Thus, the Deccan bole beds are a good analog for the phyllosilicates layers on Mars and by studying the chemistry, mineralogy and spectral properties of the Deccan bole beds, we can link their formation and alteration processes to those of martian phyllosilicates. This will provide a clearer understanding of the environmental conditions on Mars at the time of the phyllosilicates’ formation and hence during Mars’ earliest history.

Dachiardite-K (IMA No. 2015-041), a new zeolite, is a K-dominant member of the dachiardite series with the idealized formula (К2Са)(Al4Si20O48) · 13H2О. It occurs in the walls of opal–chalcedony veinlets cutting hydrothermally altered effusive rocks of the Zvezdel paleovolcanic complex near the village of Austa, Momchilgrad Municipality, Eastern Rhodopes, Bulgaria. Chalcedony, opal, dachiardite-Ca, dachiardite-Na, ferrierite-Mg, ferrierite-K, clinoptilolite-Ca, clinoptilolite-K, mordenite, smectite, celadonite, calcite, and barite are associated minerals. The mineral forms radiated aggregates up to 8 mm in diameter consisting of split acicular individuals. Dachiardite-K is white to colorless. Perfect cleavage is observed on (100). D meas = 2.18(2), D calc = 2.169 g/cm3. The IR spectrum is given. Dachiardite-K is biaxial (+), α = 1.477 (calc), β = 1.478(2), γ = 1.481(2), 2V meas = 65(10)°. The chemical composition (electron microprobe, mean of six point analyses, H2O determined by gravimetric method) is as follows, wt %: 4.51 K2O, 3.27 CaO, 0.41 BaO, 10.36 A12O3, 67.90 SiO2, 13.2 H2O, total is 99.65. The empirical formula is H26.23K1.71Ca1.04Ba0.05Al3.64Si20.24O61. The strongest reflections in the powder X-ray diffraction pattern [d, A (I, %) (hkl)] are: 9.76 (24) (001), 8.85 (58) (200), 4.870 (59) (002), 3.807 (16) (202), 3.768 (20) (112, 020), 3.457 (100) (220), 2.966 (17) (602). Dachiardite-K is monoclinic, space gr. C2/m, Cm or C2; the unit cell parameters refined from the powder X-ray diffraction data are: a = 18.670(8), b = 7.511(3), c = 10.231(4) A, β = 107.79(3)°, V= 1366(1) A3, Z = 1. The type specimen has been deposited in the Earth and Man National Museum, Sofia, Bulgaria, with the registration number 23927.

In this paper we discuss the use of mineral pigments recovered in stratigraphic position from three excavated archaeological sites (Traful Lake area, Argentina) with the aim of providing information on selection and frequency of use of these raw materials. In this region, human occupation has been recorded since 4000 BP. In order to identify the chromophoric minerals, we applied wavelength dispersive X-ray fluorescence spectrometry, Raman spectroscopy, and X-ray diffraction techniques. Green, red, yellow ochre, and white pigments dated between 3490 and 590 BP were analyzed. The results show that different analytical techniques provide complementary information in order to identify the pigments. Green, red, and yellow samples are related to iron-based compounds. The green pigments can be associated with celadonite and the others with hematite. White samples revealed the presence of hydroxyapatite. Black dots, identified as carbon, were observed in several samples. Red pigments are always predominant, and their relative abundance increases in recent strata. Results are discussed in light of the context and previous reports of chroniclers. Fil: Aldazabal, Veronica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentina Fil: Reinoso, Maria Elba. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Custo, Graciela Susana. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Cerchetti, Luciana. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Halac, Emilia Beatriz. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Polla, Griselda Ines. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Freire Espeleta, Eleonora. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Mineralogy of phosphatized and zeolitized hydrogenous cobalt-rich ferromanganese crusts from Dirck Hartog Ridge (DHR), the Perth Abyssal Plain (PAP), formed on an altered basaltic substrate, is described. Detail studies of crusts were conducted using optical transmitted light microscopy, X-ray Powder Diffraction (XRD) and Energy Dispersive X-ray Fluorescence (EDXRF), Differential Thermal Analysis (DTA) and Electron Probe Microanalysis (EPMA). The major Fe-Mn mineral phases that form DHR crusts are low-crystalline vernadite, asbolane and a feroxyhyte-ferrihydrite mixture. Accessory minerals are Ca-hydroxyapatite, zeolites (Na-phillipsite, chabazite, heulandite-clinoptilolite), glauconite and several clay minerals (Fe-smectite, nontronite, celadonite) are identified in the basalt-crust border zone. The highest Ni, Cu and Co contents are observed in asbolane and Mn-(Fe) vernadite. There is significant enrichment of Ti in feroxyhyte&minus, ferrihydrite and vernadite. The highest rare earth element (REE) content is measured in the phosphate minerals, less in phyllosilicates and Na-phillipsite. The geochemical composition of minerals in the DHR crusts supports the formation of crusts by initial alteration, phosphatization and zeolitization of the substrate basalts followed by oscillatory Fe-Mn oxyhydroxides precipitation of hydrogenous vernadite (oxic conditions) and diagenous asbolane (suboxic conditions).

Celadonite is the most abundant K-rich hydrated mineral formed during basalt alteration. In convergent margins, celadonite from the altered oceanic crust sinks into the mantle and contributes to the mantle wedge metasomatism, recorded by incompatible element enrichment in lavas and mantle xenoliths samples from these settings. However, experimental data on the role of celadonite in subduction zones as a function of P-T are still scarce. Therefore, celadonite stability under “hot” and “cold” subduction settings is investigated experimentally in this study. Results show an early silica loss, with quartz/coesite replacing celadonite from 400 to 600 °C and 2.5–7.7 GPa. At 700 °C and 2.5 GPa, celadonite is partially converted to phlogopite-annite, and at 800 °C and 4.0 GPa celadonite is absent. At temperatures above 800 °C, enstatite and phlogopite are the stable silicate phases from 2.5 to 7.7 GPa. Mossbauer spectroscopy and X-ray diffraction analyses show that the reaction of celadonite to phlogopite-annite is progressive and controlled by the Fe3+ to Fe2+ reduction in the octahedral site. Coupled to this, there is a transition of pyrite to pyrrhotite and the release of reducing fluids enriched in H2S, SiO2, OH− and K+ in the mantle wedge. These fluids have the potential to mobilize chalcophile elements (e.g. Cu, Zn) and act as mineralizing agents in shallower and more oxidizing crustal environments. Data in this study demonstrate that celadonite-phlogopite-annite series minerals are stable down to at least 230 km in the mantle, contributing to the sources of mantle metasomatism, arc-related magma genesis and possibly chalcophile mineralization.

Celadonite (K[Mg2+,Fe2+][Fe3+,Al3+](Si4O10)(OH2)) is a common void-filling mineral in ocean floor and ophiolite lavas that forms during low-temperature, off-axis, hydrothermal alteration. Its occurrence provides important information about the sink of K from seawater into the upper oceanic crust. New age determinations for celadonitic samples from a ~20 km section of the lavas in the Troodos ophiolite, along with published ages, show that most celadonite formed within the first ~20 Myrs after crust accretion. However, significant regional differences in the duration of celadonite formation are observed. In comparison to a region of flat paleo-seafloor, in a paleo-seafloor topographic low celadonite started forming later and continued forming for ~20 Myrs longer. The paleo-seafloor low is associated with abundant hydrothermal sediments which are interpreted to have played a key role in controlling the chemical conditions required for celadonite precipitation. It is hypothesised that celadonite formed for longer largely because these hydrothermal sediments acted as a source for labile Fe for a longer time than in the region where the Fe required for celadonite formation was mainly leached from silicate phases. In the region of flat paleo-seafloor, sediment did not begin accumulating for ~20 Myrs after crustal accretion allowing prolonged oxidative alteration of the upper crust. This led to Fe released by silicate phase breakdown being incorporated in stable Fe3+ containing phases, such as Fe-oxyhydroxides, rather than being transported as aqueous Fe2+ to sites where celadonite could form. If this model is correct, the uptake of K from seawater into the oceanic crust may be highly spatially heterogeneous and intimately linked to the subsurface redox conditions and the distribution of hydrothermal sediments.

A better understanding of the thermodynamics of radioactive cesium uptake at the surfaces of phyllosilicate minerals is needed to understand the mechanisms of selective adsorption and help guide the development of practical and inexpensive decontamination techniques. In this work, molecular dynamics simulations were carried out to determine the thermodynamics of Cs+ adsorption at the basal surface of six 2:1 phyllosilicate minerals, namely pyrophyllite, illite, muscovite, phlogopite, celadonite, and margarite. These minerals were selected to isolate the effects of the magnitude of the permanent layer charge (⩽2), its location (tetrahedral vs. octahedral sheet), and the octahedral sheet structure (dioctahedral vs. trioctahedral). Good agreement was obtained with the experiments in terms of the hydration free energy of Cs+ and the structure and thermodynamics of Cs+ adsorption at the muscovite basal surface, for which published data were available for comparison. With the exception of pyrophyllite, which did not exhibit an inner-sphere free energy minimum, all phyllosilicate minerals showed similar behavior with respect to Cs+ adsorption; notably, Cs+ adsorption was predominantly inner-sphere, whereas outer-sphere adsorption was very weak with the simulations predicting the formation of an extended outer-sphere complex. For a given location of the layer charge, the free energy of adsorption as an inner-sphere complex varied linearly with the magnitude of the layer charge. For a given layer charge location and magnitude, adsorption at phlogopite (trioctahedral sheet structure) was much less favorable than at muscovite (dioctahedral sheet structure) due to electrostatic repulsion between adsorbed Cs+ and the H atom of the OH- ion directly below the six-membered siloxane ring cavity. For a given layer charge magnitude and octahedral sheet structure, adsorption to celadonite (octahedral sheet layer charge) was favored over adsorption to muscovite (tetrahedral sheet layer charge) due to the increased distance to the surface K+ ions and the decreased distance to the O atom of the OH- ion directly below the surface cavity.

The paper describes the analysis of a particular kind of plaster from the walls of the Roman Sanctuary (first half of the 1st century BCE) in the centre of Brixia (now Brescia, Italy), which is an outstanding example of Roman Republican architecture. The walls were plastered and painted with different patterns, imitating marble panels and curtains. Optical microscopy on thin sections, X-ray diffraction, and infrared spectroscopy were performed on several samples of the plaster in order to reveal the execution technique. The palette consisted of glauconite, celadonite, Egyptian blue, and red and yellow ochres. In some cases, an organic compound, possibly a lipidic compound, was present in the external paint layer, as a surface treatment. The plaster contains two superimposed coats: the render coat with lime binder and sandy aggregate; the finish coat with a clay fraction (illite, chlorite, kaolinite), together with calcite from slaked lime and grains of quartz, silicate and carbonate rocks. Although Vitrivius’ De Architectura reported the use of creta (clay) as daub smeared on reed vaults, the Sanctuary of Brixia represents the first documented use in Roman buildings in a painted plaster laying on a stone masonry wall.

Gold production from the northern Pataz district in the eastern Andean Cordillera of Peru has been sourced mainly from mesothermal quartz-carbonate-sulfide veins hosted by the Mississippian Pataz batholith. Gold is also found in basement-hosted veins underlying the batholith, in the Vijus-Santa Filomena area of the district. Both are located within a central horst; similar vein mineralogy and proximal phengitic white mica alteration are common to both. However, comb-textured quartz, the chemical compositions of bulk ore and sulfide minerals, and the presence of barite and siderite veins suggest that the basement-hosted veins formed at a shallower crustal level. Similar expressions of hydrothermal alteration associated with anomalous gold, As, Sb, and Tl are also present in the adjacent Lavasen graben, where alteration is intimately associated with volcanic processes that deposited the Mississippian Lavasen Volcanics. K-Ar and 40 Ar- 39 Ar ages for hydrothermal illite from all three locations range between Mississippian and Late Triassic but are consistent with a single Mississippian hydrothermal event, if the data record a minimum age for original illite formation. The geologic setting, mineralization styles, and chemical data suggest a range of crustal depths, ranging from mesothermal batholith-hosted veins through shallow to intermediate depths for the Vijus-Santa Filomena area to a near-surface epithermal setting for the Misquichilca area. Telescoping of this 10- to 13-km crustal range into a 3-km topographic section of the Andes is attributed to syn- and postmineralization uplift and erosion. Sulfide-rich high-grade ore shoots and moderately saline fluid inclusions in the batholith-hosted veins are inconsistent with the original orogenic gold model and suggest a magmatic source component for the ore fluid, consistent with stable isotope (O, H, C, and S) compositions of quartz, illite, carbonates, and sulfides. The isotopic data suggest a mixed magmatic-meteoric ore fluid in the basement-hosted deposits of the Vijus-Santa Filomena area and the volcanic-hosted Misquichilca area. Both the Pataz batholith and the Esperanza Subvolcanic Complex are of the same Mississippian age as the hydrothermal alteration and mineralization. The Esperanza Subvolcanic Complex, comagmatic with the Lavasen Volcanics, contains cognate mineral clots from which a subjacent magma chamber can be inferred. It exhibits potassic, calc-silicate, and argillic alteration, and evidence for the evolution of an Fe-rich volatile phase. The Lavasen-Esperanza magma suite is ferroan and weakly alkaline, with A-type affinities. These features provide a conceptual genetic link with hydrothermal alteration associated with gold mineralization, including Fe (±As) sulfides, phengitic white mica, celadonite, Fe-rich carbonates, and less common Fe oxides. An oxidized intrusion-related model is proposed for gold and hydrothermal alteration in the northern Pataz district.

Remains of pictorial decorations in a series of six representative megalithic monuments of Brittany (France) and two French stelae have been studied by micro-Raman spectroscopy for the first time. Fungal colonies on the painted orthostats made it difficult to obtain in situ Raman spectra of the paint components. Nevertheless, paint micro-specimens studied in the laboratory by micro-Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electronic microscopy combined with energy dispersive X-ray spectroscopy have made possible to characterise the materials present. The minerals α-quartz, albite, microcline, muscovite, phlogopite, celadonite, beryl and anatase have been identified in the granitic rocks supporting the paintings, while dolomite and calcite are dominant in the calcareous rocky substrata. Haematite is the main component of the red pictographs, whereas amorphous carbon and manganese oxides/oxihydroxides have been used in the black ones. Calcite, gypsum and amorphous carbon have been detected as additional components of the paint in some cases. Contamination with modern tracing materials (polystyrene and e-copper-phthalocyanine blue) has been detected in several cases. The presence of pigments as decorative elements in megalithic monuments of Western France and its possible relation with those of the Iberian Peninsula create interesting expectations for the knowledge of the European megalithic culture.

We report here a study of 30 fragments of green wall paintings from Roman times found in the Patio de Banderas excavation in Seville Alcazar. The sample characterisation was realised using optical microscopy, colourimetry, infrared and micro-Raman spectroscopy, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The study of these pigments is important because it can help determine the source or the pictorial technique used. The samples studied in this work have been divided into two groups, according to the composition of their green pigments. In the first group, celadonite has been characterised as the primary component of the green colour; chlorite was also detected. Particles constituted by chromium accompanied by aluminium, iron and zinc were found in all studied samples of this group. Chlorite and chromium oxide could also be responsible for the green colour. The presence of chromium suggested the presence of green colour pigment from Verona. In the second group, a mixture of celadonite and glauconite was detected and could be responsible for the green colour observed. The addition of refracting material such as Egyptian blue was also used. A mixture of Egyptian green and Egyptian blue together with celadonite and glauconite was also found. Four classes of intonaco were recognised and classified based upon the composition of the aggregates.

The Central European Variscides and their epicontinental basins and grabens (Mesoeurope sensu Stille) subsided into the uplifted basement as well as the Alpidic Orogens, encompassing the Alpine Mts. Range, the Dinarides, the Northern Carpathians and the depressions in between (Neoeurope) are rife with a great variety of clay mineral assemblages. In many places the clay mineral deposits reach economic grade and several phyllosilicates can be used as an ore guide to non-clay mineral deposits. Time, climate and the geodynamic setting are the decisive parameters for the clay mineral accumulation. Time constitutes the x-axis for the plots illustrating the global climate change and the regional geodynamic crustal variation. It is also some kind of a yardstick to measure the preservation potential and the stability of phyllosilicates. The geological time scale is equivalent to a depth of a drill hole which penetrates different geological units characterized by various zones of post-depositional alteration. As such the geological age of formation is synonymous with an increase of the P-T regime where important boundaries concerning the micaceous phyllosilicates, kaolinite-, smectite-group minerals and the composition of glauconite are observed. The Mg-bearing phyllosilicates are marker for the Permo-Carboniferous to early Triassic and for the Middle to Late Jurassic extensional regimes in Central Europe. They indicate an ensialic geodynamic regime in Mesoeurope and an ensimatic regime in Neoeurope. This is also true for the presence and absence of Li-bearing phyllosilicates and Li-bearing tourmaline and spodumene which are a mirror image of the Permo-Carboniferous compressive regime in the Variscides and the extensional regimes in the Alpides and indicative of an ensialic and ensimatic regime, respectively. In the ensimatic geodynamic setting of the Neo- and Paratethys during the Miocene and Pliocene a felsic volcanic activity in an interarc-to back arc environment brought about an Fe-poor clay mineral assemblage in an ensimatic setting. In the ensialic Variscides only small-sized kaolinite deposits can be taken as an equivalent. Some ferroan saponite and chlorite represent the basic branch of the bimodal rift magmatic activity. Bentonitic clays and bentonites in the Alpine and Carpathian Foredeeps are marker beds for rift-related explosive volcanic activity sourced particularly in the North Atlantic Province and important mineral deposits. Fe-bearing phyllosilicates, e.g. chamosite, in the Early Ordovician and Jurassic ironstones were emplaced in a marginal and epicontinental basins, locally with restricted circulation. The Alpine extensional regimes saw the formation of celadonite in a calcareous depositional environment open to ocean. They act as facies indicators. Some phyllosilicates act as a natural multifunction display. Corrensite and mixed-layer chlorite-corrensite are not only in altered basic magmatic rocks marker for basement rocks but also affected by extraterrestrial impacts. The glauconite-kaolinite-illite-smectite-chlorite assemblages are efficient tools for the depositional environment and the post-depositional alteration, all in one. There exists an antagonism par excellence in terms of the sedimentary environment of formation between glauconite and kaolinite The clay mineral catena together with palygorskite and sudoite can be used as a proximity indicator from land to sea from the various subenvironments, e.g., from a coastal sabkha to the alluvial fan. Chromium muscovite, Cr smectite, and Cr chlorite formed at the brink from hypogene to supergene alteration and pave the way from the geodynamic/ lithofacial - to the climate-induced clay mineralization. They are the most recent clay mineral assemblages in Central Europe proved by radiometric age dating (Mio-Pliocene). The humid-tropical paleoclimate zone occurred from the Late Triassic to the Late Cretaceous, the Late Cretaceous to the Eocene, and during the Miocene. In Central Europe these paleoclimates and the resultant weathering conditions were most effective in the formation of residual clay deposits dominated by kaolin and Ni-Co laterites (garnierites) enriched in Al-, Fe- and Mn-duricrusts of economic grade. The climax of formation was reached around the Paleocene-Eocene Temperature Maximum (PETM). The tropical wet and dry paleoclimate zone in Central Europe was widespread during the Jurassic and Cretaceous leading to similar residual clay deposits impoverished in duricrusts. Residual clays in the tropical arid and semi-arid paleoclimate zones have palygorskite, corrensite and sudoite as typical phyllosilicates which denote the widespread occurrence of evaporates with the precipitation level reaching the K salt and even bittern stages. These clay minerals appeared episodically from the Late Permian through the Late Triassic. It is a paleoclimatic zone still under-explored as to Al-rich Li-Mg-bearing phyllosilicates. The high economic potential of clay minerals in Central Europe may be discovered among construction and non-construction raw materials from cement-making materials to structural clay products. Second to none are clay minerals in the construction sector used for all kinds of bricks and tiles. The majority of clay deposits is allocated to the Cenozoic, mainly Paleogene, followed by Mesozoic, Paleozoic and Precambrian rocks which is a manifesto for the expression “Clay & Time”.

A representative collection of K-dioctahedral 1M micas ranging in composition from (Mg, Fe)-poor illites to aluminoceladonites through Mg-rich illites (Fe-poor varieties) and from Fe-bearing, Mg-rich illites to celadonites through Fe-illites, Al-glauconites and glauconites (Fe-bearing varieties) was studied by Fourier-transform infrared (FTIR) spectroscopy in the middle-infrared region. Analysis and comparison of the relationships between the band positions and cation compositions of Fe-poor and Fe-bearing K-dioctahedral micas provided a generalized set of FTIR identification criteria that include the band positions and profiles in the regions of Si&ndash, O bending, Si&ndash, O stretching, and OH-stretching vibrations. FTIR data allow unambiguous identification of illites, aluminoceladonites, and celadonites, as well as distinction between Fe-illites and illites proper, as well as between Al-glauconites and glauconites. Specifically, a sharp maximum from the AlOHMg stretching vibration at ~3600 cm&minus, 1, the presence of a MgOHMg stretching vibration at 3583&ndash, 3585 cm&minus, 1, as well as characteristic band positions in the Si&ndash, O bending (435&ndash, 439, 468&ndash, 472 and 509&ndash, 520 cm&minus, 1) and stretching regions (985&ndash, 1012 and 1090&ndash, 1112 cm&minus, 1) are clearly indicative of aluminoceladonite. The distinction between Fe-illites and Al-glauconites, which have similar FTIR features, requires data on cation composition and unit-cell parameters.

International audience; Green earth is a common green pigment based on celadonite and glauconite, used since Antiquity by artists. Two geological minerals, eight commercial green earth pigments and a sample taken from a historical location in Monte Baldo were characterized. A set of different techniques including X-Ray diffraction (XRD), scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS) and numerous spectroscopies: spectrophotocolorimetry, near and mid infrared, Raman, Mössbauer were used to identify the structure and composition of the different earths. The results highlight complex composition with the presence of various phases, which can be due to the pigment sampling at a different location in the same deposit. Mobile and non-invasive analyses were carried out in order to suggest a protocol for the identification of green earth in artworks, and more specifically to distinguish celadonite and glauconite. With the available mobile non-invasive techniques, and the above analyses on the raw pigments, the green area in Nicolas Poussin’s painting, Bacchanales d’enfants (Galleria Nazionale d’Arte Antica (GNAA), Rome) was examined as a case study.

During the excavations carried out in Via di Mercurio (Regio VI, 9, 3) in Pompeii, in 2015, some red, green, black, and brown wall painting fragments were found in the preparatory layer of an ancient pavement which was probably built after the 62 AD earthquake. These fragments, derived from the rubble, were used as coarse aggregate to prepare the mortar for building the pavement. The wall painting fragments are exceptionally well preserved, which is an uncommon occurrence in the city of Pompeii. However, as they were enclosed in the mortar, the wall painting fragments were protected from the high temperatures (probably ranging between 180 °C and 380 °C) produced by the eruption in 79 AD. The pigmented outer surface of each sample was analyzed using a non-destructive multi-analytical approach, by combining spectrophotometric colorimetry and portable X-ray fluorescence with micro-Raman spectroscopy. The compositional characterization of the samples revealed the presence of cuprorivaite, goethite, and celadonite in the green pigments; hematite in the red pigments; goethite in the brown pigment; and charcoal in the black pigment. These data probably provide us with the most “faithful picture” of the various red, green, black, and brown pigments used in Pompeii prior to the 79 AD eruption.