Presence Of Hematite Research Articles

The role of low-quality calcined clay in enhancing the performance of cement mortar exposed to normal and aggressive media

This study focuses on the role of low-quality calcined Fanja (FNJ) clay in enhancing the behavior of cured cement mortar (CM) and its resistivity to chloride and sulfuric acid attack. Ordinary Portland cement was replaced with different quantities (10%, 25%, 35%, and 50% by weight) of FNJ, which was calcined at different temperatures (620 °C, 760 °C, and 900 °C). After 28 days of curing, all the hardened mortars were immersed in 5% sulfuric acid for up to 12 weeks. Additionally, a rapid chloride permeability test was conducted on the 91-day cured CM and CM-FNJ samples to evaluate the affinity of calcined FNJs to retard the chloride diffusion into CM. The results showed that all samples containing FNJ900 showed better physical and mechanical properties than the control sample, while CM with NFJ760 recorded nearly similar performance as CM-NFJ900. In contrast, the CM-FNJ620 mixtures showed lower properties than those of other mixtures. In addition to the pozzolanic reactivity of the calcined clay, the presence of hematite in the calcined clay strongly contributed to increasing the mechanical properties of the hardened mortar through forming calcium ferrosilicate hydrate binding phase, as confirmed by X-ray diffraction. Moreover, the existence of hematite increased the resistivity of CM against sulfuric acid attack as it acts as a buffer for an acidic medium. Compared with CM-FNJ900, the CM-FNJ760 is recommended for use as it exhibited a higher strength activity index and comparable resistance to accelerated chloride diffusion and sulfuric acid accompanied by lower energy demand and lower CO2 emission, achieving the concept of ‘sustainability’.

Taxonomic and functional characterization of biofilms from a photovoltaic panel reveals high genetic and metabolic complexity of the communities.

Biofilms are complex microbial cell aggregates that attach to different surfaces in nature, industrial environments, or hospital settings. In photovoltaic panels (PVs), biofilms are related to significant energy conversion losses. In this study, our aim was to characterize the communities of microorganisms and the genes involved in biofilm formation. In this study, biofilm samples collected from a PV system installed in southeastern Brazil were analyzed through shotgun metagenomics, and the microbial communities and genes involved in biofilm formation were investigated. A total of 2030 different genera were identified in the samples, many of which were classified as extremophiles or producers of exopolysaccharides. Bacteria prevailed in the samples (89%), mainly the genera Mucilaginibacter, Microbacterium, Pedobacter, Massilia, and Hymenobacter. The functional annotation revealed >12 000 genes related to biofilm formation and stress response. Genes involved in the iron transport and synthesis of c-di-GMP and c-AMP second messengers were abundant in the samples. The pathways related to these components play a crucial role in biofilm formation and could be promising targets for preventing biofilm formation in the PV. In addition, Raman spectroscopy analysis indicated the presence of hematite, goethite, and ferrite, consistent with the mineralogical composition of the regional soil and metal-resistant bacteria. Taken together, our findings reveal that PV biofilms are a promising source of microorganisms of industrial interest and genes of central importance in regulating biofilm formation and persistence.

Color Genesis and Chromatography of Yellow Silicified Corals

Color plays a vital role in revealing the formation environment and metasomatic processes of silicified coral. This study investigated the color mechanism and colorimetric characteristics of yellow silicified coral from the aspects of gemology and colorimetry. A Mako G-507C industrial camera, Raman spectroscopy, UV-Vis, EDXRF, and XRD were used for the 16 samples in this study. The results showed that the yellow color of the silicified coral was produced by Fe3+ and influenced by its degree of crystallization. The Raman peaks of all silicified corals were consistent with the standard spectral group peaks of α-quartz, where the yellow part was inferred to be goethite. The peaks at 545 and 505 nm, with a secondary peak near 435 nm in the UV-vis first-order derivative spectrum, were consistent with the presence of hematite and goethite, respectively. The band positions of the second-order derivative spectrum were shown to belong to one single-electron leap 6A1 → (4E;4A1) and one electron pair leap (6A1 +6A1) → (4T1 +4T1). The chroma and lightness were mainly affected by Fe3+. By analyzing the correlation between the Fe content and the characteristic peaks, it was found that an increase in the Fe content led to a red shift in the peak position of the main characteristic peaks, as well as an increase in the hight of the corresponding peaks in the UV-visible first-order derivative spectra. In silicified corals, an increasing crystallinity index is correlated with a decreasing phase proportion of moganite, decreasing Fe content in the bulk, and low chroma.

Examining the impact of nano‐sized Litharge, Tenorite, and Hematite on the thermal decomposition of ammonium perchlorate‐based cross‐linked composite modified double base propellant

AbstractThis study aims to compare the catalytic effects of three nano‐metal oxides (nMOs); Litharge (α‐PbO), Tenorite (CuO), and Hematite (α‐Fe2O3) on the thermal decomposition of an ammonium perchlorate based cross‐linked composite modified double base propellant (AP‐XLCMDBP). The three nMOs are synthesized via a chemical precipitation method and then characterized using XRD, FTIR, and SEM. Their effect on the thermal decomposition of AP‐XLCMDBP is studied using thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The results indicate that Litharge has no significant effect on the thermal decomposition of AP‐XLCMDBP. However, both Tenorite and Hematite nanocatalysts accelerate the thermolysis process and enhance the total heat released from AP‐XLCMDBP. Moreover, compared to Tenorite, Hematite nanoparticles are found to be a more efficient catalyst, where their presence in AP‐XLCMDBP leads to a significant decrease in activation energies of the first and the second decomposition stages by 13.67 kJ/mol and 17.57 kJ/mol, respectively. An increase of the total decomposition heat by 153.73 J/g is also attained in the presence of Hematite, displaying its high catalytic action on the thermal decomposition of AP‐XLCMDBP.

Laboratory VIS–NIR reflectance measurements of heated Vesta regolith analogs: Unraveling the spectral properties of the pitted impact deposits on Vesta

AbstractPitted impact deposits on Vesta show higher reflectance and pyroxene absorption band strengths compared to their immediate surroundings and other typical Vestan materials. We investigated whether heating to different temperatures for different durations of Vestan regolith analog materials can reproduce these spectral characteristics using mixtures of HEDs, the carbonaceous chondrite Murchison, and terrestrial analogs. We find no consistent spectral trend due merely to temperature increases, but observed that the interiors of many heated samples show both higher reflectance and pyroxene band I strength than their heated surfaces. With electron probe microanalysis, we additionally observe the formation of hematite, which could account for the higher reflectance. The presence of hematite indicates oxidation occurring in the sample interiors. In combination with heat, this might cause the increase of pyroxene band strengths through migration of iron cations. The effect grows larger with increasing temperature and duration, although temperature appears to play the more dominant role. A higher proportion of Murchison or the terrestrial carbonaceous chondrite analog within our mixtures also appears to facilitate the onset of oxidation. Our observations suggest that both the introduction of exogenic material on Vesta as well as the heating from impacts were necessary to enable the process (possibly oxidation) causing the observed spectral changes.

How iron-bearing minerals affect the biological reduction of Sb(V): A newly discovered function of nitrate reductase

As a toxic element of global concern, the elevated concentration of antimony (Sb) in the environment has attracted increasing attention. Microorganisms have been reported as important driving forces for Sb transformation. Iron (Fe) is the most important metal associated element of Sb, however, how Fe-bearing minerals affect the biological transformation of Sb is still unclear. In this study, the effects of Fe-bearing minerals on biological Sb(V) reduction were investigated by employing a marine Shewanella sp. CNZ-1 (CNZ-1). Our results showed that the presence of hematite, magnetite and ferrihydrite (1 g/L) resulted in a decrease in Sb(III) concentration of ~19–31 % compared to the Fe(III)-minerals free system. The calculated Sb(V) reduction rates are 0.0256 (R2 0.71), 0.0389 (R2 0.87), 0.0299 (R2 0.96) and 0.0428 (R2 0.95) h−1 in the hematite-, magnetite-, ferrihydrite-supplemented and Fe(III)-minerals free systems, respectively. The cube-shaped Sb2O3 was characterized as a reductive product by using XRD, XPS, FTIR, TG and SEM approaches. Differential proteomic analysis showed that flagellar protein, cytochrome c, electron transfer flavoprotein, nitrate reductase and polysulfide reductase (up-regulation >1.5-fold, p value <0.05) were supposed to be included in the electron transport pathway of Sb(V) reduction by strain CNZ-1, and the key role of nitrate reductases was further highlighted during this reaction process based on the RT–qPCR and confirmatory experiments. Overall, these findings are beneficial to understand the environmental fate of Sb in the presence of Fe-bearing minerals and provide guidance in developing the bacteria/enzyme-mediated control strategy for Sb pollution.

Mineralogical analysis and firing temperature of the ancient potteries of Tamil Nadu using spectroscopic techniques

Our curiosity about archaeological artefacts leads us to discover details about the lifestyles of our ancestors. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDX), and thermogravimetry differential thermal analysis (TG-DTA) techniques have been used to characterize the ancient potteries unearthed at the recently excavated archaeological site of Palayanur, Tamil Nadu. Minerals such as quartz (silicate group), feldspar, clay minerals (illite), calcite, hematite, magnetite, and organic carbon were identified from FT-IR analysis. Quartz had been detected in all of the samples, as evidenced by the significant absorption peaks at 794 cm−1, 795 cm−1, 779 cm−1, 780 cm−1, 781 cm−1, and 695 cm−1. The obtained 2θ values from the XRD spectrum validated the mineral’s presence as well as the pottery’s firing condition and temperature. The presence of calcite indicates that these samples were fired below 850 ℃, and the presence of hematite in the potteries indicates that they were fired in an oxidizing atmosphere. The elemental concentration and microstructure of collected pottery samples were determined by the SEM-EDX technique to elucidate the nature of the raw material used for making pottery samples.

Prediction of acid production potential of self-combusted coal mining wastes from Douro Coalfield (Portugal) with integration of mineralogical and chemical data

The prediction of acid production potential (APP) of coal waste piles that underwent self-combustion was investigated by integrating mineralogical and chemical data to secure a sustainable environment. Burned and unburned material from three waste piles in Douro Coalfield (Portugal) were studied to understand the effect of self-combustion on APP. For this purpose, mineralogical analysis, paste pH, infrared spectroscopy, acid ammonium oxalate leaching, and nitric acid leaching were performed to determine the most reliable APP scores, while British Columbia Research Initial test was carried out for the neutralization potential (NP) determination. The major acid producers were pyrite and jarosite, while the neutralizers were calcite, aragonite, azurite, siderite and hydrotalcite as rare accessory minerals. Hence, APP scores were determined in terms of the calculation factors of pyrite and jarosite. A thermal transformation from jarosite to hematite was detected due to self-combustion. The presence of hematite and mullite minerals in extremely burned wastes is in the foreground. After obtaining APP and NP, net acid production potential (NAPP) scores were calculated and subsequently interpreted with net acid generation (NAG) test results. The NAPP scores between 0.7 and 24.1 kg CaCO3/t were obtained, while the negligible level of NP scores was between 0.1 and 1.6 kg CaCO3/t. According to six different acid mine drainage (AMD) screening criterion, most of samples were detected as “potentially acid forming”. The interpretation of “non-acid forming” was not concluded for any wastes. Consequently, the piles are moderately prone to form AMD, and the NAPP in extremely burned zone of the piles is lower than the zones of partially burned and unburned due to the loss of sulfide and scarcity of acid sulfates.

The effect of cross-linker structure on interfacial interactions, polymer dynamics and network composition in an epoxy-amine resin

Understanding interactions at the polymer / metal oxide interface is central to improving the performance lifetime of corrosion resistant coatings, where network polymers commonly form via step growth mechanisms in the presence of pigments. Here we employ a holistic analytical approach encompassing ATR-FTIR, DSC and molecular dynamics simulations to consider how crosslinker structure affects adsorption and incorporation into the network, using a stoichiometric mixture of diglycidylether of bisphenol-A (DGEBA) with m-xylylenediamine (MXDA) cured in the presence of hematite (Fe2O3) and goethite (FeOOH) powders. We find that the rigid MXDA molecule has two distinct binding modes on both hematite and goethite, and that synergistic hydrogen bonding modes observed on goethite limit interconversion between the two. Moreover, we find that binding persists in fully cured composite samples, determining the levels of residual amine. In contrast to previously reported results using triethylenetetramine (TETA) crosslinkers, however, we find that the Tg of composite specimens is independent of added hematite and goethite volumes. Molecular dynamics simulations demonstrate this is due to electrostatic binding between the cationic Fe sites and electronegative heteroatoms in MXDA. This renders both amine functionalities unavailable for incorporation into the network and hence, unlike TETA, MXDA adsorption does not determine polymer dynamics.

Hematite-promoted nitrate-reducing Fe(II) oxidation by Acidovorax sp. strain BoFeN1: Roles of mineral catalysis and cell encrustation.

Although nitrate-reducing Fe(II) oxidizing (NRFO) bacteria can grow sustainably in natural environments, numerous laboratory studies suggested that cell encrustation-induced metabolism limitations and cell death occurred more seriously in the absence of natural minerals. Hence, a study on how natural minerals could affect NRFO is warranted. This study examined the impact of hematite on NRFO by Acidovorax sp. BoFeN1 with different electron donors (acetate and Fe(II), acetate alone, and Fe(II) alone) and with nitrate as an electron acceptor. When acetate and Fe(II) were used as the electron donors, the amount of Fe(II) oxidation and nitrate reduction was enhanced in the presence of hematite, whereas no promotion was observed when only acetate was added as an electron donor. Under the conditions with only Fe(II) added as an electron donor, the level of Fe(II) oxidation was increased from 3.07 ± 0.06 to 3.92 ± 0.02 mM in the presence of hematite and nitrate reduction was enhanced. This suggests that hematite promotes microbial nitrate reduction by accelerating the biological oxidation of Fe(II). The main secondary minerals were goethite and lepidocrocite. After adding hematite, the assemblage of iron minerals on the cell surface decreased, and the cell crusts became thinner, indicating that hematite effectively mitigated cell encrustation. Furthermore, hematite accelerated the chemical oxidation of Fe(II) by nitrite. Hence, hematite can promote the NRFO of Acidovorax sp. BoFeN1 via two possible pathways: (i) hematite acts as nucleation sites to mitigate cell encrustation; (ii) hematite catalyzes the biological and chemical oxidation of Fe(II) through the mineral catalysis effects. This study highlights the importance of existing iron minerals on NRFO and sheds light on the survival strategy of NRFO bacteria in anoxic subsurface environments.

Evaluation of the Ability of Rhizobacterial Isolates to Solubilize Sparingly Soluble Iron Under In-vitro Conditions

One of the problems of calcareous soils is the lack of absorbable iron for plants grown in these areas. Research by various researchers has shown that some rhizosphere-dwelling microorganisms have the ability to solubilize resources containing low-soluble iron and conversion it to soluble and absorbable for the plants. Different mechanisms such as proton secretion, production of organic acids, and production of siderophore can be effective in solubilizing low-soluble iron. Accordingly, in this study, the potential of twenty rhizobacteria for solubilizing low-soluble iron sources (eg, iron phosphate, hematite, and goethite) has been evaluated. The experiment was performed under in-vitro condition in a completely randomized design with three replications. According to the results, three isolates, namely, ZP15, ZC10, and ZP13 were characterized as promising isolates. In the presence of iron phosphate, the concentration of solubilized iron by isolates ZP15, ZP13, and ZC10 was 5.19, 4.35, and 4.27 mg/l, respectively. These values for the isolates ZC10 and ZP13 in the presence of hematite was recorded 6.49 and 5.35 mg/l, respectively, and in the presence of goethite was 7.02 and 6.70 mg/l, respectively. The amount of siderophore production for the three isolates ZP15, ZC10, and ZP13 was 16.47, 17.1, and 31.55 µM, respectively. The high-performance liquid chromatography analysis revealed that the most important acids produced by these isolates were 2-ketogluconic acid (303.8 µg/ml) for ZP15, oxalic acid (246.9 µg/ml) for ZC10, and gluconic acid (100.2 µg/ml) for ZP13, respectively. The molecular and biochemical identification of these three isolates ZP15, ZC10, and ZP13 showed that they belong to the genera Stenotrophomonas, Pantoea, and Agromyces, respectively.

MINERALOGICAL AND GEOCHEMICAL FEATURES OF LIMESTONES OF THE KATAV FORMATION OF THE AKTASH AREA (YAMANTAU ANTICLINORIUM, SOUTHEN URAL)

A mineralogical and geochemical study of limestones of the Katav Formation was carried out, outcrops of which are noted in the Yamantau anticlinorium 8–10 km northwest of Muradymovo settlement on Aktash Area. In the mineralogical composition of limestones, a relatively high content of quartz (4–15 %), presence of small amounts (at the level of 1 %) of dolomite and K-feldspar, variable contents (0.3–1.6 %) of hematite, as well as a constant admixture of chlorite and albite (1–7 %). The presence of hematite in the limestones is considered as possible mineralogical evidence in favor of arid conditions and evaporate sedimentation settings during the Katavian. The contents of F, Cl, V, Cr, Ni, Sr in limestones are below the clarke values, Pb is close to the clarke, Cu, Zn, Zr are 1.5–2 times higher than the clarke. The Clarke values of Co (4 times) and Ba (19 times) are the highest. The established features of the distribution of the halogen elements fluorine and chlorine (extremely low concentrations, their absence of association with calcite, and a high positive correlation with micaceous minerals, which apparently have an epigenetic origin) cannot be considered as evidence of evaporite sedimentation environments in the Katav time.

Inhibition of hematite on acid mine drainage caused by chalcopyrite biodissolution

Even though biodissolution of chalcopyrite is considered to be one of the key contributors in the formation of acid mine drainage (AMD), there are few studies to control AMD by inhibiting chalcopyrite biodissolution. Therefore, a novel method of using hematite to inhibit chalcopyrite biodissolution was proposed and verified. The results indicated that chalcopyrite biodissolution could be significantly inhibited by hematite, which consequently decreased the formation of AMD. In the presence of hematite, the final biodissolution rate of chalcopyrite decreased from 57.9% to 44.4% at 20 day. This in turn suggested that the formation of AMD was effectively suppressed under such condition. According to the biodissolution results, mineral composition and morphology analyses, and electrochemical analysis, it was shown that hematite promoted the formation and accumulation of passivation substances (jarosite and Cu 2− x S) on chalcopyrite surface, thus inhibiting the biodissolution of chalcopyrite and limiting the formation of AMD.

Iron speciation in soil size fractions under different land uses

Iron (Fe) (oxyhydr)oxides represent a significant phase for the organic carbon (OC) stabilization. Due to their high surface areas, short-range-ordered Fe minerals, like ferrihydrite, show a higher ability to stabilize OC than crystalline secondary minerals, like lepidocrocite, goethite, and magnetite. However, how Fe phases and their crystallinity relate to soil organic matter (SOM) composition is still not completely known. We investigated Fe solid phase speciation in two soil particle size fractions (i.e., fine sand — FSa — and fine silt and clay — FSi + Cl —), isolated from coniferous (CF) and broadleaved forest soils (BF), grassland soils (GL), and technosols (TS). All samples were characterized by Fe K-edge extended X-ray absorption fine structure (EXAFS) and X-ray diffraction, and a subset by 57Fe Mössbauer spectroscopy. Further, ramped combustion thermal analyses (coupled differential scanning calorimetry (DSC) and CO2 evolved gas analysis (CO2-EGA)) were used to evaluated SOM stability. With the only exception of TS, goethite was the main Fe phase in FSa fractions, whereas less crystalline phases (i.e., ferrihydrite, based on EXAFS) dominated the FSi + Cl fractions. The proportion of goethite and ferrihydrite in both fractions decreased with increasing OC content, while that of Fe(III)-SOM in FSa increased with increasing OC content. Mössbauer and EXAFS data clearly indicated a presence of hematite in GL soils. Our data suggest that more crystalline Fe forms, like goethite and hematite, may be important for OC abundance in the FSa fraction and in soils with high OC contents, like GL. Thermal analysis showed the dominance of mineral associated organic matter in low-OC soils, and of plant residues in high-OC soils. As a whole, we posit that the FSi + Cl fractions contain Fe phases of less crystallinity because of presumed association with SOM, and that SOM in the FSi + Cl fraction is also more thermodynamically stable than in FSa, although differences are observed across land uses. Our observations suggest that the nature of Fe-SOM interactions can vary substantially with soil particle size and land use, which has important implication for SOM persistence.

Multidisciplinary characterization of the “Ghiara” volcanic paleosoil (Mt. Etna volcano, Italy): Petrologic characters and genetic model

The large expanses of lava field and soils spread out around Mt. Etna volcano (Italy), make unique the landscape of the whole area. In this work, we investigated a sample set of a peculiar aggregate locally named with the term “Ghiara” collected in different outcrops of Mt. Etna volcano southern flank. A distinctive character of this material is that it is found exclusively beneath solidified lava flows. In past centuries, Ghiara was widely employed in construction field for its reddish hue and the high pozzolanic activity; for the same reasons it has now raised the interest of the scientific community involved in the formulation and production of eco-friendly materials as alternative to the traditional ones. The aim of this paper is to define its chemical and mineralogical characters and to provide a model for its genesis. We conducted a multidisciplinary analytical approach, complementary to the few investigations reported in literature, in order to define the chemical compositions by means of X-ray fluorescence (XRF), the mineralogy through synchrotron radiation X-ray diffraction (XRD) analyses and spectroscopic features by Raman and Fourier-transform infrared (FT-IR) methods. The analytical results show that the original Etnean paleosoils, mainly given by pyroclastic fall and accumulation, underwent marked modifications that produced the unique mineral assemblage of the Ghiara, characterized by the presence of hematite, a mineral responsible for its reddish appearance. The heterogeneity of the samples, however, does not allow us to define a univocal genetic model. On the basis of the outcrops geometry and the environmental conditions we propose a range of models that fit the characters of each sample. In detail, the genesis of this material can be influenced by one or all the following phenomena: i) chemical oxidation, ii) biological oxidation and iii) hydrothermal transformation by interaction of meteoric waters with volcanic volatiles from lavas. This work represents a first contribute in the knowledge of Ghiara characters and genesis, which on one side will help to a better use in its employment for construction purposes, on the other will contribute to constrain the hematite formation processes in different environments.

Combined MA-XRF, MA-XRPD and SEM-EDX analysis of a medieval stained-glass panel formerly from Notre Dame, Paris reveals its material history

As part of its conservation-restoration, the 13th century stained-glass panel ‘the Annunciation’, was examined at the micro- and macro level. This window, since 1898 in the collection of the Museum Mayer Van den Bergh (Antwerp, B), was formerly a part of the southern Rose window of the Notre Dame Cathedral (Paris, F). The insigths emerging from a first phase of the analysis, comprising non-invasive analysis techniques such as optical microscopy combined with macroscopic X-ray fluorescence (MA-XRF) and X-ray diffraction (MA-XRPD) mapping, were used to select sampling positions for the second phase of investigation that involved micro-invasive analysis, namely scanning-electron microscopy coupled to energy-dispersive X-ray analysis (SEM-EDX). The aim of the investigation was fourfold: (1) to assess the applicability of MA-XRF scanning for the characterisation of stained glass windows prior to any conservation or restoration procedure, (2) to assess the applicability of MA-XRPD scanning to identify the degradation products formed on the surface of stained glass windows, (3) to establish a method to limit the set of sampled glass fragments taken from a glass panel for quantititive analysis while maintaining sufficient representativeness and (4) to distinguish the original glass panes and grisaille paint from non-original glass panes that were inserted during various past interventions. Most of the panes in this window proved to consist of medieval potash glass, consistent with the 13th c. origin of the window while a limited number of panes were identified as non-original infills, with divergent glass compositional types and/or colorants. Most panes derive their color from the pot metal glass (i.e. homogenously colored) they were made of. Some of the panes that originally had a red flashed layer on their surface, completely or partially lost this layer due to weathering. Three main compositional glass families with similar color could be defined. With the exception of the yellow and orange panes, the chromophoric elements responsible for the dark(er) and light(er) blue (Co), green (Cu), purple (Mn) and red colors (Cu) were identified. Two different grisaille paints were encountered, part of which were restored during the 19th century. On the basis of this information, all missing pieces were replaced by glass panes with appropriate colors and the panel could be successfully conserved to its former glory. On the surface of several panes, typical glass degradation products such as calcite, syngenite and gypsum were identified, together with lead based degradation products such as anglesite and palmierite. In addition, the presence of hematite and melanotekite in the grisailles was observed; also the presence of Zn, uncorrelated to Cu, in the grissailes on the right side of the window became apparent.

Structural Breakdown of Natural Epidote and Clinozoisite in High-T and Low-P Conditions and Characterization of Its Products

A heat treatment was performed on selected epidote and clinozoisite crystals to establish the nature of any changes in the optical and crystal-chemical properties and to identify a breakdown product using a wide spectrum of analytical methods. Natural samples were heated from 900 to 1200 °C under atmospheric pressure in ambient oxidation conditions for 12 h. Epidote and clinozoisite were stable at 900 °C; those heated at 1000 °C, 1100 °C, and 1200 °C exhibited signs of breakdown, with the development of cracks and fissures. The average chemical composition of epidote is Ca2.000Al2.211Fe0.742Si2.994O12(OH), while that of clinozoisite is Ca2.017A12.626Fe0.319Si3.002O12(OH). The breakdown products identified by electron microanalysis, powder X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy were anorthite, pyroxene compositionally close to esseneite, and wollastonite. The decomposition of the epidote-clinozoisite solid solution is controlled by the following reaction: 4 epidote/clinozoisite → 2 pyroxene + 2 wollastonite + 4 anorthite + 2 H2O. Pyroxene likely contains a significant proportion of tetrahedral Fe3+ as documented by the Mössbauer spectroscopy. Moreover, the presence of hematite in the Mössbauer spectrum of the clinozoisite sample heated at 1200 °C can result from the following reaction: 4 epidote → pyroxene + 3 wollastonite + 4 anorthite + hematite + 2 H2O.

Microstructural evaluation of the cement stabilization of hematite-rich red soil

Red soil, composed of a clayey bed containing hematite, is used as pavement material in southern Iran. As an effective and economical technique, soil improvement with cement is common practice for improving the engineering properties of different soil and pavement layers. The formation of nanostructured calcium silicate hydrate (C-S-H) is the primary factor contributing to this improvement. On the other hand, the presence and dissolution of hematite in the soil structure can also influence C-S-H formation. The present study investigates the effects of cement on the engineering properties of the hematite-rich red soil from a microstructural point of view, with particular emphasis on changes in the C-S-H nanostructure. For this purpose, red soil specimens were stabilized with 2, 4, 6, 8 and 10 wt% cement for different curing times. The soil's engineering properties were evaluated by macrostructural testing, namely by soil particle size analysis and slake durability, water absorption, Unconfined Compressive Strength (UCS), and Ultrasonic Pulse Velocity (UPV) tests. Furthermore, the soil stabilization process and the effects of hematite on the C-S-H microstructure were evaluated by pH and Electrical Conductivity (EC) tests, X-Ray Diffraction (XRD), energy-dispersive X-ray analysis (EDX), and Scanning Electron Microscope (SEM) imaging. It was shown that adding cement to hematite-rich soil promotes Calcium Ferrite Hydrate (C-F-H) and ilavite (C-F-S-H) formation and, consequently, improves the red soil's stability and compressive strength. In fact, using 6 wt% cement, the presence of hematite, and the formation of Fe-containing nanostructures helped the red soil specimen develop a compressive strength of 2.04 MPa (17 times that of the natural soil) in seven days.

Spectroscopic analysis of vintage hand-colored real photo postcard of French stage actress Melle Charclais by Reutlinger, Paris

This article reviews the history of real photo postcards and hand-coloring practices to draw attention to their historical and artistic value, and the significance of their preservation. A real photo postcard of French stage actress, Melle Charclais, dating back to the early 1900s’ and taken by Léopold Reutlinger, a famous German photographer, was selected to acquire knowledge on the materials and techniques used at the time to develop an understanding of their deterioration paths; and accordingly, make correct preservation choices. This particular real photo postcard was chosen for its esthetic value since it represents an unusual art nouveau style of postcard designs integrating photography with hand-coloring and bead art. The photographic process used was identified as silver gelatin process using a USB digital microscope. Analyses performed using scanning electron microscopy with energy-dispersive X-ray spectroscopy, attenuated total reflectance—Fourier transform infrared spectroscopy and Raman spectroscopy revealed the presence of Hematite, Cobalt Blue, and Naples Yellow.

Late Miocene magmatic‐hydrothermal system and related Cu mineralization of the Arakawa area, Akita, Japan

AbstractThe Northeast Japan arc hosts a number of hydrothermal vein‐type copper deposits associated with Neogene felsic intrusions. The Arakawa area is underlain by Cretaceous granites and Tertiary sedimentary rocks, which were intruded by the Miocene Ushizawamata dacite. Zircon grains from the dacite intrusion yield a 206Pb/238U intercept age (laser ablation inductively coupled plasma mass spectrometry) of 8.10 ± 0.30 Ma, consistent with a previously reported K‐Ar illite age (8.1 ± 0.4 Ma) of the Ushizawamata lead and zinc prospect in the Arakawa area. The dacite intrusion and the surrounding Miocene sedimentary rocks were altered by hydrothermal activity on the surface, classified into four alteration zones: (1) biotite‐chlorite, (2) illite, (3) chlorite and (4) smectite, centered on the intrusion. About 20 major vertical sub‐parallel copper‐bearing quartz veins occur in the chlorite alteration zone on the west side of the dacite. The first vein stage is composed of chalcopyrite and chamosite with a minor amount of quartz in brecciated wall rocks, and the second‐stage is characterized by the presence of hematite in addition to the first‐stage mineral assemblage. The third‐stage consists of comb‐shaped quartz veins with a minor amount of chalcopyrite, sphalerite, galena and pyrite, and the fourth‐stage of barite and apatite present in druse in the third‐stage veins. Primary fluid inclusions in quartz of the first‐ and third‐stages are all liquid‐rich and two‐phase. Homogenization temperature and salinity of first‐stage quartz are 263–277°C and 5.7–7.5 wt% NaCl equivalent (eq.); in quartz of the third‐stage, 251–270°C and 2.7–4.2 wt% in the inner zone and 207–250°C and 2.7–3.7 wt% in comb‐shaped quartz on the vein margin. The fluid inclusions in quartz phenocrysts of the Ushizawamata dacite show two distinct assemblages, halite‐bearing polyphase inclusions that coexist with vapor‐phase inclusions and/or vapor‐rich two‐phase inclusions, and liquid‐rich two‐phase inclusions. Homogenization temperature and salinity of the polyphase inclusions are higher than 401°C and 46.7 wt%, respectively, and those of the vapor‐rich two‐phase inclusions report 393–419°C and 2.6–3.7 wt% NaCl, whereas the liquid‐rich two‐phase inclusions returned 344–403°C and 8.0–9.3 wt%, respectively. These results indicate that the ore forming fluid was slightly cooler and lower in salinity than the late‐stage hydrothermal fluid in the Ushizawamata intrusion. The spatial and temporal proximity between the Ushizawamata dacite and the hydrothermal veins indicates that the dacitic magma was genetically related to the vein copper mineralization in the Arakawa area.