Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite



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Checa, Antonio G. and Bonarski, Jan T. and Willinger, Marc G. and Faryna, Marek and Berent, Katarzyna and Kania, Bogusz and González-Segura, Alicia and Pina Martínez, Carlos Manuel and Pospiech, Jan and Morawiec, Adam (2013) Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite. Journal of the Royal Society of Interface, 10 (86). ISSN ISSN: 1742-5689, ESSN: 1742-5662

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The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy–electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic unit sare single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occurmainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface anddo not showpreferential tilting along anyof the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, inwhich the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is amatter of future research.

Item Type:Article
Uncontrolled Keywords:Crystallography, Biomineralization, Bivalves, Calcite, Electron back-scatter diffraction
Subjects:Sciences > Geology > Crystallography
ID Code:50878
Deposited On:24 Jan 2019 11:54
Last Modified:09 Jun 2020 11:11

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