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Search query: mineral weathering
19 articles match your search "mineral weathering"Results 1 to 10, sorted by relevance:
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The twinned structure of the new uranium oxide mineral was refined from X-ray diffraction data and was found to contain fluorine and pentavalent uranium. The presence of pentavalent uranium is indicative of the reducing conditions under which the mineral formed. Nollmotzite is the first naturally occurring uranium oxide mineral that contains fluorine.
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A methodological approach is presented for computing the structural formula of clay minerals from transmission electron microscopy–energy-dispersive X-ray spectroscopy (TEM-EDX) data of individual particles, including pure and complex interstratifications. The combination of TEM-EDX and modelling of XRD patterns enables the refinement of the TEM-EDX-based structural formula. This methodology allows identification of the mineral composition and mineral transformations happening in both geological and industrial processes.
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The crystal structure of the low-temperature 2O polytype of CuII3TeVIO6 (the mineral mcalpineite) has been determined by 3D electron diffraction (3D ED) and Rietveld refinement following X-ray powder diffraction (PXRD).
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We report high-pressure neutron powder diffraction measurements of the most hydrated phase in the MgSO4–H2O system, magnesium sulfate undecahydrate, including an analysis of the elastic strain tensor and observations concerning phase changes that occur at high pressure.
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A neutron diffraction study of the nuclear and magnetic structure of goethite (
-FeOOH) with varying crystallinity and temperature is presented. The antiferromagnetic structure in the Pb′nm color space group suggests spins aligned parallel to the c axis. A significant reduction in the Néel temperature was found for a nanocrystalline sample.
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A combined approach of scanning 3D X-ray diffraction and phase contrast tomography has been used to study the hydration of calcium sulfate hemihydrate to form gypsum. This approach was found to be a powerful tool that permitted – for the first time – coupling of detailed crystallographic and morphological information on the hemihydrate–gypsum transition observed in situ.
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Experimental investigations of Mg K-edge XANES analysis of geologic materials are presented. The energy positions and resonance features obtained from these spectra can be used to specify the dominant molecular host site of Mg.
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A method to enhance the X-ray diffraction signal of a specific targeted crystalline phase within a sample is presented. This technique can be implemented in a handheld or in-line instrument format.
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The entrance to the Zaouïa Moulay Idriss II in Fez, Morocco, contains the only known example of a dodecagonal quasiperiodic cartwheel pattern in Islamic art. Its geometry satisfies the dodecagonal Ammann quasilattice and is close to the geometry of a diffraction pattern from a dodecagonal quasicrystal.
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The crystal structure of the uranyl-phosphate mineral phurcalite is characterised by extensive hydrogen bonding. It comprises a less common type of H2O bonding in solids: a transformer H2O unit (with a three-coordinated O atom), which is not directly linked to any metal cation. This study documents the advantage of combining XRD data and TORQUE calculations, which are significantly less demanding of resources than DFT calculations..