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  • 1
    Keywords: X-rays Diffraction ; X-rays Diffraction ; Konferenzschrift ; Beugung ; Pulver ; Kristall ; Röntgenbeugung ; Pulver ; Debye-Scherrer-Methode ; Beugung
    Type of Medium: Book
    Pages: XI, 369 S. , graph. Darst.
    ISBN: 0939950243
    Series Statement: Reviews in mineralogy 20
    DDC: 548.83
    RVK:
    RVK:
    Language: English
    Note: Literaturangaben
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 18 (1984), S. 35-42 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Farfan, G. A., Apprill, A., Cohen, A., DeCarlo, T. M., Post, J. E., Waller, R. G., & Hansel, C. M. Crystallographic and chemical signatures in coral skeletal aragonite. Coral Reefs. (2121), https://doi.org/10.1007/s00338-021-02198-4.
    Description: Corals nucleate and grow aragonite crystals, organizing them into intricate skeletal structures that ultimately build the world’s coral reefs. Crystallography and chemistry have profound influence on the material properties of these skeletal building blocks, yet gaps remain in our knowledge about coral aragonite on the atomic scale. Across a broad diversity of shallow-water and deep-sea scleractinian corals from vastly different environments, coral aragonites are remarkably similar to one another, confirming that corals exert control on the carbonate chemistry of the calcifying space relative to the surrounding seawater. Nuances in coral aragonite structures relate most closely to trace element chemistry and aragonite saturation state, suggesting the primary controls on aragonite structure are ionic strength and trace element chemistry, with growth rate playing a secondary role. We also show how coral aragonites are crystallographically indistinguishable from synthetic abiogenic aragonite analogs precipitated from seawater under conditions mimicking coral calcifying fluid. In contrast, coral aragonites are distinct from geologically formed aragonites, a synthetic aragonite precipitated from a freshwater solution, and mollusk aragonites. Crystallographic signatures have future applications in understanding the material properties of coral aragonite and predicting the persistence of coral reefs in a rapidly changing ocean.
    Description: This project was funded by the Mineralogical Society of America Edward H. Kraus Crystallographic Research Fund and the WHOI Ocean Ventures Fund. G. Farfan was supported by a National Science Foundation Graduate Research Fellowship Grant No. 1122374 and a Ford Foundation Dissertation Fellowship. Sample collections from R. Waller were funded under NSF Grant Numbers 1245766, 1127582 and NOAA Ocean Exploration Deep Atlantic Stepping Stones. The authors thank Erik Cordes for the samples collected from the Gulf of Mexico, which were supported by NSF BIO-OCE Grant # 1220478. STZC collections from A. Apprill were funded by a Dalio Foundation (now ‘OceanX’) and a KAUST-WHOI Special Academic Partnership Funding Reserve with Christian Voolstra. Research and coral collections in Cuba were conducted under the LH112 AN (25) 2015 license granted by the Cuban Center for Inspection and Environmental Control with the assistance of Patricia Gonzalez and Michael Armenteros. Corals from Western Australia were collected under license number SF009558 obtained by M. McCulloch, and from the Maldives Ministry of Fisheries and Agriculture with collection permits (No. (OTHR)30-D/INDIV/2013/359). Matthew Neave assisted with the collections.
    Keywords: Aragonite ; Crystallography ; Geochemistry ; Biomineralization ; Environmental mineralogy ; Coral skeleton
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2012-01-01
    Description: The presence of boron in the structure of diamond is rare in nature, and even when present, reported values are =0.5 ppm. This study used various spectroscopic methods and time-of-fight (ToF-) SIMS to characterize and analyze for boron in natural type IIb blue diamonds, including the well-known Hope and the Blue Heart diamonds, and on one high-pressure, high-temperature annealed natural stone. Infrared spectroscopy measurements reveal uncompensated boron values as large as 1.72 ± 0.15 ppm, which is significantly higher than the previously reported maximum of 0.5 ppm. ToF-SIMS analyses gave spot total boron concentrations as high as 8.4 ± 1.1 ppm for the Hope diamond to less than 0.08 ppm in other blue diamonds. By comparison, a type Ia diamond did not show detectable boron. ToF-SIMS analyses revealed strong zoning of boron in some diamonds, which was confirmed by mapping the uncompensated boron using synchrotron infrared spectroscopy. This greater range of boron concentrations compared to previous studies might be explained by the larger number of natural diamonds analyzed here, 78, compared to
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
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  • 5
    Publication Date: 2011-04-01
    Description: The positions of hydrogen (deuterium) cations within the interlayer of synthetic Na- and K-birnessite samples have been determined for the first time using Rietveld analysis and Fourier difference syntheses, from time-of-flight powder neutron diffraction data. This study revealed that two symmetry-related D(H) positions are located ~1 A above and below the midpoint between the split O interlayer sites in Na-birnessite. This result confirms our earlier interpretation that the split interlayer sites include O atoms from two symmetrically equivalent H2O molecules. These molecules are oriented 180{degrees} to each other, and they are pivoted about a single set of H(D) atoms positions. The interlayer H2O molecules in K-birnessite are oriented such that one of the H(D) atoms is pointed approximately toward the Mn octahedral layer O atoms and the other is directed approximately within the net of interlayer K/O sites. In K-birnessite, six K-Ooct distances are shorter than 3.35 A, compared with only two Na-Ooct bond lengths in Na-birnessite, suggesting that K cations are more tightly bonded to the octahedral O atoms than are Na cations.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
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  • 6
    Publication Date: 2011-01-01
    Description: The crystal structure of braitschite, Ca6.15Na0.85RE2.08[B6O7(OH)3(O,OH)3]4(H2O), is reported here in space group P6/m with unit-cell parameters a = 12.1506(6), c = 7.3678(4) A, and V = 942.03(8) A3. Data were collected from a single crystal using a MoK{alpha} source and a CCD detector, solved by direct methods, and refined to an R factor of 2.81%. The mineral structure consists of hexaborate fundamental building blocks that polymerize along [001] and are bound by Ca2+ and REE3+ counter-ions. The framework forms hexagonal channels, which are occupied alternately by Ca2+ cations and water molecules. In an investigation of its thermal stability, braitschite maintains its crystallinity to a temperature of 400 {degrees}C, after which it undergoes decomposition. Using Rietveld refinements against powder X-ray diffraction data, we were able to track the loss of water molecules in channels and hydroxyl groups in the covalent B-O network with increasing temperature.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
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