Celia Marcos Pascual

University of Oviedo | UNIOVI · Department of Geology

With the purpose of obtaining synthetic materials from other natural sources for industrial and technological applications, a thermal alteration study was carried out with commercial vermiculites of different purity and origin. For this objective, samples were subjected to 1000 °C in a furnace both at ambient and reduced (N2/Ar) atmospheres. The th...

The proposal of this research was to obtain products with higher porosity and specific surface area than the raw vermiculite for its possible application as a support material for CO2 adsorption. In addition, it was proposed to analyze the possible geological implications of the products resulting from the hydrothermal treatment of vermiculites in...

The characteristics of the electromagnetic waves and the electromagnetic spectrum are recalled, emphasizing the visible spectrum, in which the relationship between the different units used for their description is shown. The characteristics of visible light propagation as a wave movement are established. From one of the solutions of this equation,...

Provides a lucid introduction to crystalline materials such as terrestrial minerals Enhances your understanding of Earth's processes both in the crust and mantle Includes exercises that illustrate the basic concepts of crystallography

Two types of studies were carried out on the lithic materials found in stratigraphic unit 6 of Los Canes cave used by Mesolithic human groups: (1) quantification of the retouched and nonretouched lithic materials to determine the adaptive strategy in relation to changes in the availability and technology resources and (2) crystallographic/mineralog...

Effect of water immersion at different times (from 1/2h to 24 h) on raw and expanded vermiculite from Uganda was investigated. The expansion was carried out by electrical heating at different temperatures and by irradiation with microwaves. After, the expansibility (k) and the water absorption content (WA) were obtained and the samples were charact...

Two commercial vermiculites from China and Libby were treated with different alcohols (methanol, ethanol, propanol and butanol) at room temperature for up to one month and afterwards irradiated with microwaves. The exfoliated and non-exfoliated particles were characterized by X-ray diffraction, high-resolution transmission microscopy, thermal gravi...

Chert samples from different coastal and inland outcrops in the Eastern Asturias (Spain) were mineralogically investigated for the first time for archaeological purposes. X-ray diffraction, X-ray fluorescence, transmission electron microscopy, infrared and Raman spectroscopy and total organic carbon techniques were used. The low content of moganite...

The aim of this study was to investigate the efficiency of removing Cr 6+ from aqueous solutions using two exfoliated vermiculite: (1) heated abruptly at 1000 • C and (2) irradiated with microwave radiation. The effects investigated were contact time, adsorbate concentration and initial Cr 6+ concentration. The adsorption with both exfoliated vermi...

Vermiculite is a layered silicate mineral with 2:1 crystalline structure and a broad diversity in charged layers associated with numerous isomorphic substitutions, disorder effects, dehydration–rehydration ability and swelling processes. Vermiculites are more abundant and much cheaper compared to other clays, with the same benefits. Therefore, they...

The relationship between textural parameters (specific superficial area (S BET) and porosity (V p)) of lamellar products obtained from HNO 3-activated vermiculites and their iron and water content has been established. Two commercial vermiculites, one thermoexfoliated commercial vermiculite, and one pure vermiculite were nitric-acid-treated at 4 an...

Depending on the treatment, the crystallinity increase of vermiculite may be accompanied by the enhancement of the majority starting phase, and the crystallinity loss may be accompanied by the appearance or disappearance of interstratified phases. Starting vermiculites with high K+ content in the interlayer have more interstratified phases and lowe...

This work aimed at investigating the adsorption of Cr6+ in water by exfoliated vermiculite. The adsorbant tested in this experiment was a vermiculite (from China) which has been subjected to heating at 1000 °C for 1 minute, resulting in an exfoliated vermiculite. Three effects were studied: 1) contact time; 2) initial concentracion of Cr6+; 3) adso...

The aim of the present study was to investigate the removal efficiency of oleic acid from aqueous solutions by thermally expanded and hydrophobized vermiculites. The expansion of the samples was carried out in a furnace at 1000 °C for 2 min. The hydrophobization using polymethyl-hydro-siloxane as hydrophobing derivatizing reagent was performed by i...

As a continuation of our previous study, in this work, we investigated the effects of propanol and butanol treatments and subsequent irradiation with microwave on commercial vermiculites. No expansibility was observed after propanol or butanol treatments (k = 1.0). Samples treated with propanol or butanol and subsequently irradiated with microwaves...

The aim of the present study was to investigate the effect of thermal expansion on the removal efficiency of commercial vermiculites towards Ni2 + ion from aqueous solutions. Three effects were studied: 1) Contact time between the adsorbent and Ni2 + dissolved in the retention process; 2) adsorbent mass; 3) concentration of Ni2 + in adsorption. Ni2...

Present work reports the alcohol treatment and subsequent irradiation with microwave of commercial vermiculites. Alcohol treatment resulted in slight delamination of the layers and the color of the samples changed into brilliant golden and no expansibility was observed (k ≤ 1.3). Samples treated with alcohol and subsequently irradiated with microwa...

Vermiculite is a layered silicate with a complex crystalline structure, as it is characterized by the existence of a large density of defects even in the case of the most pure vermiculite [e.g., Santa Olalla, Huelva (Spain)]. As a result of their lamellar structure, vermiculite structures present a broad diversity of behavior and are interesting fr...

In previous investigations on the magnetic properties of Ni2 +-vermiculite intercalation compounds from Santa Olalla, it was considered that each of the two anomalies in the real component of the ac magnetic susceptibility exhibited by these compounds could be related to the spin dynamics of the nickel ions located in different local environments i...

New results obtained from X-ray diffraction about structural transformations induced by vacuum between the different hydration states of three vermiculites (powdered and flake samples) with different composition and origin, are presented. The dehydration process of the vermiculites under vacuum has been proved to be the same as that of temperature...

We report on the magnetic properties of a Ni(2+)-vermiculite intercalation compound from Santa Olalla, Huelva (Spain). This modified vermiculite was studied by means of DC and AC magnetic measurements. The existence of two maxima in magnetic susceptibility below 10 K was interpreted in terms of the Cole-Cole formalism as being due to spin-glass fre...

Herein we report on synthetic iron-intercalated vermiculites prepared from a Mg-vermiculite mineral from Santa Olalla, Huelva, Spain, by means of an ion exchange process from aqueous solutions of FeCl2 and FeCl3. Thermogravimetric, X-ray diffraction, magnetic susceptibility and Mössbauer spectral studies have been used to characterize the synthetic...

The effect of microwave power on the expansion of vermiculites was studied at 800W for different microwave exposure times (from 10s to 600s) and compared with the changes after heating to 1000°C and dehydration in vacuum. The interlayer water molecules of the individual flakes were driven off quickly by microwave irradiation separating the layers....

The church of Santa María del Naranco is an important monument from the pre-Romanesque period of Asturian art. Here we present research that locates the probable source of travertine used in the construction of a vault within this monument. Since the genesis of this travertine is associated with spring activity, and archival evidence suggests that...

Commercial vermiculites from different places were studied in order to know the cause of their different behaviour after abrupt heating at 1000 °C. Mössbauer spectroscopy provided Fe2+ and Fe3+ contents and allowed identification of both tetrahedral and octahedral iron. The Fe2+ content was higher in type-2 vermiculites (with K+− or > 1 and/or Na+...

ABstrAct A sample of Mg-vermiculite from Santa Olalla (Spain) was studied by X-ray powder diffraction, electron microprobe, and thermo-gravimetry. The 3D structure is described as a disordered stack of two types of 2D building blocks, which are made up of one talc-type layer and one interlayer space containing hydrated Mg 2+ cations. We have succee...

A specimen of Mg-vermiculite from Santa Olalla (Spain) has been investigated. Powder diffraction data has been simulated and an experimental pattern refined by means of the DIFFaX+ software. The best modelling is obtained assuming the mineral to possess bidimensional periodicity instead of a tridimensional one: the structure can be described as a d...

Microtextural studies are often the basis for projects proposing improvements in the quality of refractory coatings that come into contact with aggressive molten material. The material used for this analysis either comes from laboratory-level corrosion tests or from furnace walls and linings that have come to the end of their working cycle. This a...

Los estudios microestructurales han estado frecuentemente en la base de proyectos orientados a la mejora en la calidad de los revestimientos refractarios destinados a estar en contacto con metales fundidos. Los materiales empleados en este trabajo proceden de las paredes de hornos que están en la fase final de su vida útil. El trabajo intenta asoci...

For the purpose of knowing the vermiculites which would have larger capability to retain contaminating substances heating commercial samples from different places have been identified and their thermal behaviour at several temperatures has been investigated by X-ray diffraction (XRD), electron microprobe, thermal analysis (TG and DTA), scanning ele...

Mineral particles could have influenced on the climate of Oviedo, a non-industrial city situated in the centre of an industrial zone of the North of Spain, increasing the temperature and the precipitations, in spite of the fact that “greenhouse gases” concentrations have diminished in this city in recent years. The directive (1999/30/EC) of the Eur...

The {001} surfaces of three vermiculite samples from different geological origins have been examined with an atomic force microscope (AFM) in the contact mode of operation. Images of the basal O plane of the sheet of tetrahedra and the plane of OH groups of the octahedral sheet of the Mg-interlayer were recorded. Differences in the appearence of th...

The Nodal Wear Model (NWM) constitutes a tool of applicable work study the processes of differential corrosion in the Peirce – Smith convertor (PSC) with the purpose of reaching significant improvements in duration and productivity of the several alternatives that one could utilize of the coating. For the application of the NWM to CPS is necessary...

New results obtained from X-ray diffraction about structural transformations induced by vacuum between the different hydration states of three vermiculites (powdered and flake samples) with different composition and origin, are presented. The dehydration process of the vermiculites under vacuum has been proved to be the same as that of temperature...

The Nodal Wear Model (NWM) constitutes a tool of applicable work study the processes of differential corrosion in the Peirce - Smith convertor (PSC) with the purpose of reaching significant improvements in duration and productivity of the several alternatives that one could utilize of the coating. For the application of the NWM to CPS is necessary...

Nodal Wear Model in the corrosion Peirce - Smith copper convertor The Nodal Wear Model (NWM) constitutes a tool of applicable work study the processes of differential corrosion in the Peirce - Smith convertor (PSC) with the purpose of reaching significant improvements in duration and productivity of the several alternatives that one could utilize o...

Structural transformations between the different hydration states of three vermiculite samples from Sta. Olalla (Huelva, Spain), Paulistana (Piaui, Brasil) and West China, have been observed by X-ray diffraction at atmospheric pressure, P = 1.4 x 10 –2 mbar and P = 2.4 x 10 –4 mbar. The samples were studied in flake and powder forms. The effect of...

En este trabajo se han caracterizado mineralogica y texturalmente tres refractarios monoliticos bajo diferentes condiciones de calentamiento -sinterizacion, con el objeto de conocer su evolucion. La caracterizacion mineralogica se ha realizado con difraccion de rayos X, microscopia optica y microsonda electronica. La caracterizacion textural se ha...

In this work three monolithic refractories with different thermal conditions -sintering have been characterized mineralogical and texturally in order to know its behaviour. The mineralogical characterization has been made by X-ray diffraction, optic microscopy and electron microprobe. The textural characterization was carried out by image analysis...

Flavonol and berillium selective polymers were prepared using the molecular imprinting technique. Some of their microstructural characteristics were evaluated by atomic force microscopy. The molecular recognition capabilities of the prepared polymers were evaluated by optical transduction in a flaw-through system. The results showed that imprinted...

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and...

Structural, chemical, physical and micrascopic characteristics of emerald, alexandrite and phenakite fram Franqueira (Spain) are presented, and their gemmological possibilities are discussed. Comparison of data between Franqueira emeralds and Ural Mountains emeralds is emphasized, because both deposits contain the same associations of beryllium min...

This paper reports the results obtained in a study of the crystal structure of two villamaninite samples from Villamanin (Leon, Spain), labeled (1) and (2). Villamaninite, (Cu,Ni,Co,Pe)(S,Se)(2), is a pyrite-type disulfide. Different long-period elements, including Au, in ionic substitution are also observed. Previous authors have assumed a cubic P...

When crystals grow under convection conditions, the hydrodynamic environment can promote the formation of inclusions in the rear side of the crystals, downstream in relation to the fluid flow. An experimental study of this mechanism of fluid trapping is presented, and the conditions under which hydrodynamics influences growth behaviour are discusse...

This paper summarizes the main tectonic, mineralogical, petrological and geochemical features of the three peralkaline complexes located in the southern end of the Malpica-Tuy Unit, in Galicia (NW Spain). The Porriño and La Guía complexes occur in metasedimentary rocks, mainly graywackes, of the Iberian Massif, while the Piñeiro complex is hosted b...

The Franqueira deposit is the first documented example of a gem-quality chrysoberyl, emerald, and phenakite deposit in Western Europe. It is located in the northwestern part of the Iberian Peninsula, in the Galicia -Tras os Montes zone, which is made up of two domains: (1) schistose rocks, including mafic-ultramafic overthrusted complexes, and (2)...

This paper summarizes the main tectonic, mineralogical, petrological and geochemical features of the three peralkaline complexes located in the southern end of the Malpica-Tuy Unit, in Galicia (NW Spain). The Porrino and La Guia complexes occur in metasedimentary rocks, mainly graywackes, of the Iberian Massif, while the Pineiro complex is hosted b...

Iwounometie semeue melte Pieselmomills »Men 111(1111 I. lenell/m Orna-bionssalM IhNow cm emewsma 11W~ ai lab~~ &elide TM*44411Mdes 3-toweearsos nos mns /poema! tilmillwiNis • • T. ome. ~IN 09 ♦ seedo me ~re M. rig. 1 Situation and generalised geologic map of the franqueira ore.

The aim of this peer is to ci~yibe the geolcgical, rineralogical and geocheadcal rerarks of the Frarqueira pegratitic miraralizations giving raise to a genetíc descriptiva redel. Ebccretasoratic interactiai of Berich pegratitic rridies with dbnitic wall-rocks leads to the déveloprent of gerstcne decsit, several reters thidc, formad essentilly of er...

The aim of this pape r is to describe the geological, mi.neralogical and geochemica.l. remarks or the franqueira pegmatitic mineralizations giving raise to a genetic DESCRIPTIVE model. Exometasomatic interaction of Be-rich pegmatitic bodies with dunitic wall-rocks leads to the development of gemstone deposit, several meters thick, formed essentiall...

Abstract: Stolzite (PbW04), tetragonal, isomorphous with wulfenite and dimorphous with raspite, occurs in La Tala (Salamanca, Spain). The mineral formed as a supergene alteration product of lead-bearing hydrothermal veins crosscutting calcsilicate metasediments locally enriched in tungsten. Its scheelite-type crystalline structure has been resolved...

We show the steps followed for obtaining the principal reflectances of an absorbing uniaxial mineral, ilmenite, by use of the inference method derived from statistical reflectance parameters of the sample. The values obtained in air, at 580 nm, with this method are: R =19.60.3 and R =17.80.3.

The indicating surface of natural reflectance for absorbing uniaxial media is studied in this paper. Expressions for the maximum, minimum, mode and median of the distributions of natural reflectances have been obtained. In order to obtain accurate values of the mean natural reflectance and its standard deviation, it is necessary to resort to numeri...

In order to evaluate the errors which can be introduced in the measurement of reflectance, we have made a study of data obtained for several minerals and in two immersion media on turning the microscope stage to a succession of positions relatively orientated by 45°. Fourier analysis of the results allows an estimate of the different errors as a fu...

A computer program has been developed which allows a refinement of reflectance measurements on polished grain mounts of absorbing minerals, using Fourier analysis. The observed reflectances of each section are obtained from eight measurements, by rotating the stage through 45° sectors. Statistical processing of the results, corresponding to 100 ran...

Fourier's trigonometric interpolation method was used to compare the anisotropy of reflectivity with that of microhardness on random polished sections of ilmenite, hematite and wolframite. Reflectivity was measured over the range 460-700 nm using a microphotometer and hardness was measured by a static indentation method. The samples were checked by...

One ofthe classical traits of the prehistory of Asturias is the extensive use of other lithic raw materials as an alternative to flint. This feature, clearly related to the searcity of this rock in the predominantly Palaeozoic landscape of the region, is characteristic of the Upper Palaeolithic tool kits. Yet it clearly increases during the Mesolit...