Search results for "hematite"
showing 10 items of 60 documents
Textural-chemical changes and deformation conditions registered by phyllosilicates in a fault zone (Pic de Port Vieux thrust, Pyrenees)
2017
International audience; Synkinematic phyllosilicates in fault zones can be used to deduce the deformation mechanisms and the conditions of fault activity, as their chemical composition, crystal structure and texture can record the different stages of deformation and fluid-rock interactions. The Pic de Port Vieux, a second-order thrust related to the major Gavarnie thrust in the southern central part of the Pyrenees Axial Zone, juxtaposes Triassic pelites of the hanging wall and Cretaceous limestones of the footwall. In order to investigate the mineralogical and geochemical changes and constrain the deformation conditions of thrusting, characterization of phyllosilicates was performed along …
Ocre, hematites y óxido de hierro: el problema terminológico = Ochre, Hematite and Iron Oxid: The Terminological Issue
2016
Los óxidos de hierro son prácticamente omnipresentes al analizar contextos, no solo referentes al arte rupestre, sino también en relación con toda una serie de actividades que podríamos considerar cotidianas en ambientes prehistóricos. Sin embargo, su estudio sistemático no ha comenzado hasta tiempos muy recientes. Fruto de ello, podría decirse que una parte de la literatura arqueológica no especializada en el campo de la pigmentología muestra, en ocasiones, cierta inexactitud terminológica. Con este documento pretendemos, a través de un análisis tanto de su funcionamiento, como de las propiedades geoquímicas y mineralógicas del ocre, la hematites y los propios óxidos de hierro, exponer la …
IDENTIFICATION, PROCESSING AND USE OF RED PIGMENTS (HEMATITE AND CINNABAR) IN THE VALENCIAN EARLY NEOLITHIC (SPAIN)
2012
The results of the first elemental and structural physicochemical analyses (SEM–EDX, TXRF, XRD, FTIR, GC and EDXRF) of Early Neolithic red pigment samples from the region of Valencia confirm one of the earliest uses of cinnabar (HgS) in Spain (5300 to 5000 cal bc). They also inform on the storage of massive quantities of hematite and the development of specific technologies of hematite-based paint production and use. The samples were recovered at the three most significant Early Neolithic sites of the Mediterranean coast of Spain: Cova de l'Or (Beniarres, Alacant), Cova de la Sarsa (Bocairent, Valencia) and Cova Fosca (Vall d'Ebo, Valencia), which together have provided the most important E…
Mössbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit's journey through weakly altered olivine basalt on the plains and pervasiv…
2006
The Moessbauer spectrometer on Spirit measured the oxidation state of Fe, identified Fe-bearing phases, and measured relative abundances of Fe among those phases for surface materials on the plains and in the Columbia Hills of Gusev crater. Eight Fe-bearing phases were identified: olivine, pyroxene, ilmenite, magnetite, nanophase ferric oxide (npOx), hematite, goethite, and a Fe(3+)-sulfate. Adirondack basaltic rocks on the plains are nearly unaltered (Fe(3+)/Fe(sub T) Px), and minor npOx and magnetite. Columbia Hills basaltic rocks are nearly unaltered (Peace and Backstay), moderately altered (WoolyPatch, Wishstone, and Keystone), and pervasively altered (e.g., Clovis, Uchben, Watchtower, …
Chemical composition and complex refractive index of Saharan Mineral Dust at Izaña, Tenerife (Spain) derived by electron microscopy
2007
Abstract Samples from two strong homogeneous dust plumes from the Saharan desert reaching Izana (Tenerife, Spain) in July and August 2005 were taken with a miniature impactor system and filter samplers. Size, aspect ratio and chemical composition of more than 22,000 individual particles were studied by scanning electron microscopy. The mineralogical phase composition of about 200 particles was investigated by transmission electron microscopy. In addition, the aerosol size distribution was measured with an optical particle spectrometer. In all samples, the aerosol was dominated by mineral dust with an average composition (by volume) of 64% silicates, 6% quartz, 5% calcium-rich particles, 14%…
Fe Mossbauer spectroscopy as a tool in astrobiology
2006
The element Fe and Fe-bearing minerals occur ubiquitously throughout the field of astrobiology. Cycling between the various oxidation states of Fe provides a source of energy available for life. Banded iron formations may record the rise of oxygenic photosynthesis. The distribution of Fe between Fe-bearing minerals and its oxidation states can help to characterize and understand ancient environments with respect to the suitability for life by constraining the primary rock type and the redox conditions under which it crystallized, the extent of alteration and weathering, the type of alteration and weathering products, and the processes and environmental conditions for alteration and weatheri…
Mineralogy and geochemistry of Terra Rossa soils, western Sicily: insights into heavy metal fractionation and mobility
1996
Abstract The distribution of heavy metals in typical Terra Rossa soils and their partitioning in specific soil phases are estimated on the basis of the comparative evaluation of bulk contents, results from sequential chemical extraction procedure (SEP) and scanning electron microscopy/energy dispersive X-ray analysis ( SEM EDX ). A general natural enrichment of heavy metals with respect to average soil is observed. Cadmium proves to be remarkably high (up to 2.4 ppm). Large amounts of Fe, Cr, Cu, Ni, Pb, and Zn occur in the ‘residual’ fraction. The results indicate selective accumulation of the heavy metals in Fe oxides, present as hematite, goethite and maghemite. There is good evidence th…
Multianalytical Approach to explain the darkening process of hematite pigment in paintings from ancient Pompeii after accelerated weathering experime…
2013
[EN] In this paper, recently excavated fresco painting fragments from the House of Marcus Lucretius (Pompeii) and not exposed to the atmosphere since the eruption of the Mount Vesuvius were subjected to a controlled SO2 atmosphere and high relative humidity. These experiments were conducted in order to simulate under accelerated conditions the possible deterioration of the hematite pigment and plaster. The mineralogical transformation of the polychromy and plaster was monitored using mainly Raman spectroscopy, a non-destructive technique, but also infrared spectroscopy (FT-IR) and scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS). After different exposure cycles to…
The influence of phosphoric acid on steel and on its corrosion products: a Mössbauer spectroscopic approach
1983
Mossbauer spectroscopy was used to study corroded iron after treatment with phosphoric acid or commercial rust transformers. It was found that treatment produced normal iron phosphates from metallic iron, hematite and FeO, and acid ferric phosphate FeH 3 (POI4I)I2I. 2.5H 2 O from alphaand gamma Fe 2 O 3 and alpha, beta, and gammaFeOOH. When these last are present, phosph oric acid treatment does not produce a protective, inhibiting layer. See also AATA 19-702. -- AATA
Study of the annealing conditions and photoelectrochemical characterization of a new iron oxide bi-layered nanostructure for water splitting
2016
Iron oxide nanostructures have emerged as promising materials for being used as photocatalysts for hydrogen production due to their advantageous properties. However, their low carrier mobility and short hole diffusion length limit their efficiency in water splitting. To overcome these drawbacks, in the present study, we synthetized a new hematite (alpha-Fe2O3) bi-layered nanostructure consisting of a top nanosphere layer and a nanotubular underneath one by electrochemical anodization. Annealing parameters such as temperature, heating rate and atmosphere were studied in detail in order to determine the optimum annealing conditions for the synthetized nanostructure. The obtained new bi-layere…