Influencia del Grupo Fosfato en la Morfología de los Cristales de Calcita (CaCO3)

La cristalización del CaCO3 es un tema que suscita un gran interés en diversos contextos, desde la biomineralización a la cristalización industrial, pasando por la precipitación de carbonatos en medios naturales de baja temperatura. Es un hecho contrastado que la presencia de ciertas impurezas en el medio de cristalización puede tener un efecto marcado sobre la selección polimórfica del CaCO3 y sobre la morfología de los cristales que se desarrollan. Aunque existen numerosos estudios sobre el efecto de impurezas inorgánicas sobre la cristalización del CaCO3, la mayor parte de los mismos se ha centrado en el papel de impurezas catiónicas. Sin embargo, estudios recientes (Fernández-Díaz et al., 2010) han demostrado que la presencia de altas concentraciones de sulfato en el medio de cristalización favorece la formación de vaterita e inhibe su posterior transformación en el polimorfo estable calcita. Por otro lado, Sánchez- Pastor et al. (2011) ha descrito un intenso efecto del grupo aniónico cromato sobre la morfología de los cristales de calcita, que desarrollan caras de prismas y se alargan paralelamente al eje c al aumentar la concentración de este anión en el medio. En este mismo volumen, Fernández-González et al. (2011) describen un efecto similar del grupo seleniato sobre el hábito de los cristales de calcita.Peer reviewe

Challenges to rutile-based geoscientific tools: low-temperature polymorphic TiO2 transformations and corresponding reactive pathways

Rutile, a common accessory mineral in a wide variety of rocks, is the most stable naturally occurring TiO2 polymorph. The relationship between its trace element composition and formation conditions has provided geoscientists with discriminant tools for fingerprinting geological processes, such as magmatic evolution and subduction zone metamorphism, alongside applications to the study of sediment provenance. In the present work, volcaniclastic rock samples belonging to Fara and Saiq Formations, outcropping in Jebel Akhdar mountains, Oman, are studied with Raman spectroscopy and Electron Microprobe (EMP) aiming: of (i) the identification of different naturally-occurring TiO2 polymorphs, (ii) the evaluation of their trace element contents in relation with hydrothermal alteration features, and (iii) the analysis of the mineral reactive pathways behind the observed textural relationships. Raman investigations demonstrated that interstitial, fine-grained TiO2 corresponds to anatase, whereas rutile occurs as isolated single grains. EMP determinations further revealed that an identified Nb-enrichment in anatase is coupled with a corresponding Nb-depletion in rutile. The combination of the obtained results with petrographic observations enabled unravelling the TiO2 reactive pathways affecting the studied samples. Thus, a coupled polymorphic dissolution-precipitation reaction assisting rutile-to-anatase conversion has been defined, together with the role of Nb in further stabilizing the structure of the lower temperature polymorph. Semi-quantitative thermometric considerations suggest that rutile substrates are likely of magmatic origin, whereas anatase formation is clearly associated with a lower temperature aqueous environment. The gathered results raise fundamental questions concerning the application of commonly used rutile-based geochemical and thermometric tools

Human body biominerals: Interdisciplinary proposal for the Biology and Geology in High School

Pocos aspectos de las Ciencias de la Tierra y la vida, impartidos en Bachillerato, muestran las interrelaciones entre la Geología y la Biología. Además, los estudiantes españoles valoran, en general, mejor la Biología que la Geología, por la concurrencia de diversos factores como el desconocimiento de la Geología por su menor carga lectiva, los temarios excesivamente teóricos de esta, la escasa relación entre ambas ciencias o el mejor conocimiento que tienen de las salidas laborales de la Biología. En este trabajo revisamos el currículo estatal de Bachillerato para encontrar los bloques en los que es posible introducir una visión interdisciplinar relacionada con la Cristalografía y la Mineralogía, cuya enseñanza actual es poco integrada y motivadora como muestran diversos estudios. Proponemos diversos contenidos que se podrían abordar en las programaciones de aula relacionando los biominerales del cuerpo humano (huesos, dientes, etc.) y sus características mineralógicas y cristalográficas con su función anatómica y fisiológica. Los objetivos son, por una parte, utilizar la buena valoración de cuestiones sobre anatomía para introducir conceptos de Mineralogía menos conocidos y, por otra, motivar al alumnado por su estudio y valoración mostrando la importancia de estos en investigaciones y salidas laborales emergentes como la Geología Médica.Competency-based learning have been proved to be an effective learning method characterized by developing and applying specific skills that can then be used to obtain the required knowledge. Thus, the process of teaching and learning should be undertaken by combining active-learning and collaboration to help to retain the knowledge. Therefore, a multidisciplinary vision in which each professional contribute with a specific topic would be necessary. Few topics of the Earth and Life Sciences, taught in Spanish education, show the interrelations between Geology and Biology. On the other hand, Spanish students generally value Biology better than Geology, due to the combination of many factors such as the little presence of Geology in the curricula, the scarce relationship between these two sciences, the extremely theoretical classes or the greater knowledge that students have of job opportunities in the field of Biology. In this paper we revise the curricula of Spanish Bachelors degree (students from 16 to 18 years old) to find issues that can present an interdisciplinary vision related to Crystallography and Mineralogy, in which current learning is non integrated nor motivating as many studies show. We propose some contents that can be included in relation to the human body biominerals (bones, teeth,…), their mineralogical characteristics and their anatomical and physiological functions. The main objectives are to use the good valuation of anatomical topics to introduce lesser-known concepts of Crystallography and Mineralogy, and at the same time to motivate the students to study and value these Geology fields emphasizing their importance in emerging research fields and new work opportunities such as Medical Geology.Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu

The effect of CO2-3 on the growth of barite {001} and {210} surfaces: An AFM study

The growth of barite {001} and {210} faces from aqueous solutions moderately supersaturated with respect to barite (βbarite ≈ 12 for experiments on {001} surfaces and βbarite ≈ 7 for experiments on {210} surfaces) and bearing different concentrations of carbonate has been studied in situ using an atomic force microscope (AFM). Nanoscopic observations show that, above a certain carbonate concentration threshold in the aqueous solution, the advancement of monolayers (~3.5Å in height) on barite {001} and {210} surfaces is strongly inhibited. However, inhibition never affects the growth of the first monolayer, whose growth rate increases in the presence of carbonate. In contrast, the second monolayer growth rate decreases as the concentration of carbonate in the solution increases. For high carbonate concentrations in the solution, growth stops after the formation of the first monolayer. While on barite {001} faces, the formation of a second monolayer does not occur for carbonate concentrations higher than 0.2 mM, on barite {210} faces the complete inhibition of the second monolayer is observed for carbonate concentrations higher than 0.05 mM. Once growth on {001} or {210} faces is completely inhibited, i.e. such surfaces are in the ‘‘dead zone’’, growth can be recovered by increasing supersaturation. In order to study the recovery behaviour of barite {001} and {210} faces from the ‘‘dead zone’’, an additional series of AFM experiments have been conducted. In these experiments, carbonate-free aqueous solutions with increasing supersaturations with respect to barite were passed over {001} and {210} surfaces previously ‘‘poisoned’’ with carbonate. Our experimental results show that the recovery of growth on barite {001} faces requires an important increase of the solution supersaturation. In contrast, the recovery of barite {210} surface growth does not require any supersaturation increase, but spontaneously occurs in a few minutes. Our observations of inhibition and growth recovery on barite surfaces at a nano-scale are discussed and compared with the descriptions given by the classical crystal growth inhibition models

Agregados biomiméticos de calcita crecidos en hidrogel de gelatina: Efecto combinado del Mg y la concentración de sólido en el gel

Comunicación presentada al Congreso SEM 2015, XXXV Reunión Científica de la Sociedad Española de Mineralogía, Huelva 30 junio -3 julio de 2015.Gran parte de los procesos de mineralización que tienen lugar en el seno de los organismos vivos se desarrollan en matrices de naturaleza gelatinosa ricas en polisacáridos y proteínas. Los hidrogeles sintéticos comparten muchas de las características que exhiben estas matrices orgánicas (Asenath-Smith et al., 2012). Además, es posible ajustar la preparación de los hidrogeles para que las condiciones fisicoquímicas en su seno sean similares a las que se dan en los ambientes de biomineralización en organismos (Nindiyasari et al., 2014a). La calcita, el polimorfo de CaCO3 estable en las condiciones reinantes en la superficie terrestre, es uno de los componentes más abundantes de los tejidos mineralizados de los organismos fósiles y modernos. La mayor parte de los tejidos duros calcíticos de origen marino contienen magnesio, que se encuentra incorporado en la estructura de la calcita sustituyendo al calcio. Los contenidos de magnesio de los biominerales varían normalmente entre 0 y 23 % molar, aunque alcanzan valores significativamente más altos en casos concretos. Por ejemplo, algunas partes de los dientes de los erizos de mar contienen un 45% molar de MgCO3. En este trabajo se presenta un estudio sobre las características de la cristalización de carbonato cálcico en hidrogeles de gelatina preparados con distinta concentración de sólido y, por tanto, con distinta densidad y rigidez, y que pueden contener magnesio o no en la disolución acuosa que rellena sus poros. La investigación realizada se ha centrado en el análisis de las características composicionales, morfológicas y microtexturales de los cristales y agregados cristalinos de calcita obtenidos en los experimentos, así como en el estudio de las características de la matriz de hidrogel que queda ocluido en ellos durante la cristalización. El estudio del efecto que esta matriz tiene sobre el desarrollo de microtexturas en los cristales y agregados es otro de los núcleos de este trabajo.Esta investigación ha sido financiada por la Acción Integrada Hispano Alemana (AIB2010 DE-0008, DAAD- 50749739) y de los proyectos CGL2010- 20134-C02-01 y 2013-47988-C2-1-P. Se agradece el apoyo del Centro Nacional de Microscopia, del servicio central de difracción (UCM) y del laboratorio de Espectroscopia Raman (MNCN, CSIC).Peer reviewe

Vaterite Stability in the Presence of Chromate

Vaterite aggregates grown in Cr(VI)-bearing silica gel were studied by combining scanning electron microscopy and Raman spectroscopy. All the vaterite samples were spherical aggregates consisting of lens-shaped individuals, and their morphology was distinctive for vaterite. Raman spectra corresponding to the aggregates grown in gels containing high Cr(VI) concentrations showed the typical bands of vaterite. However, in contrast to their morphology, the Raman spectra of the aggregates grown in the presence of lower Cr(VI) concentrations exclusively showed bands characteristic of calcite. These aggregates are interpreted as calcite pseudomorphs formed after vaterite through a replacement process. The replacement involves the interface coupling of the dissolution of vaterite and the precipitation of the stable polymorph calcite. The fact that only those vaterite aggregates formed in the presence of low Cr(VI) concentrations transformed into calcite indicates the presence of high Cr(VI) concentrations in the growth medium contributes to stabilize vaterite and prevents its transformation into calcite in the short term

XIMET – The Trans-University Educational Materials Exchange-Network with a Focus on Genetics

XiMET (Xarxa d'intercanvi de Materials Educatius Transuniversitària) es una red de innovación educativa y calidad docente formada por profesorado perteneciente a las Universidades de Valencia (UVEG), Universidad Politécnica de Valencia (UPV), la Universidad de Barcelona (UB) y la Universidad Autónoma de Madrid (UAM). Dicha red se ha establecido para la difusión de las acciones realizadas por el profesorado del departamento de Genética de la UVEG dentro de los grupos GEMEG y BIOPAC, y además facilitar la activación de alianzas de innovación interuniversitaria. Una tarea fundamental de XiMET es la elaboración de materiales docentes y objetos de aprendizaje multimedia, diseñados como apoyo para la docencia.XiMET (Xarxa d'intercanvi de Materials Educatius Transuniversitària) is a network of university teachers working on different aspects of Evolutionary Biology, and which has been established with the aim of promoting the spread of educational innovation partnerships within Spain. The Network is formed by teaching staff belonging to the University of Valencia (UVEG), Polytechnic University of Valencia (UPV), University of Barcelona (UB) and the Autonomous University of Madrid (UAM). Developing activities (e.g. joint meetings) with the support of faculty from multiple universities is an important and necessary step to optimize the efforts of teachers from different centers, but also a key factor in assessing the different skills and concepts that the student receives in each University. Therefore, a fundamental task of XiMET is the creation of a collection of teaching materials and multimedia learning objects (MLOs) designed as a support for teaching. These MLOs will facilitate the work in the classroom for the different modules offered in our universities and will further complement the work carried out within the theory lectures

Raman Study of Synthetic Witherite–Strontianite Solid Solutions

Characterization of zoned crystals of a synthetic witherite–strontianite solid solution (BaxSr1-xCO3) was carried out using electron microprobe analysis and Raman spectroscopy. The sample was obtained by coprecipitation using the silica gel method. As each carbonate crystal from this preparation showed the whole range of intermediate compositions BaxSr1-xCO3, 0.1≤x≤0.9, the solid solution could be studied for single crystals. Peak-shape analysis of the Raman bands showed that the peak shifts depend on the replacement of the Ba and Sr cations introducing different radii and masses. We observed a shift to higher wave numbers for an increase of the SrCO3 content