Structure and crystallography of foliated and chalk shell microstructures of the oyster Magallana: the same materials grown under different conditions
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Springer Nature
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2018Referencia bibliográfica
Checa González, A.G.; Harper, Elizabeth M.; González Segura, A. Structure and crystallography of foliated and chalk shell microstructures of the oyster Magallana: the same materials grown under different conditions. Scientific Reports. (2018) 8:7507. [DOI:10.1038/s41598-018-25923-6].
Patrocinador
Funding was provided by projects CGL2013-48247-P and CGL2017-85118-P (to A.G.C., E.M.H. and A.G.-S.) of the Spanish Ministerio de Economía, Industria y Competitividad. A.G.C. also acknowledges the Research Group RNM363 (Junta de Andalucía).Resumen
Oyster shells are mainly composed of layers of foliated microstructure and lenses of chalk, a highly
porous, apparently poorly organized and mechanically weak material. We performed a structural and
crystallographic study of both materials, paying attention to the transitions between them. The
morphology and crystallography of the laths comprising both microstructures are similar. The main
differences were, in general, crystallographic orientation and texture. Whereas the foliated
microstructure has a moderate sheet texture, with a defined 001 maximum, the chalk has a much
weaker sheet texture, with a defined 011 maximum. This is striking because of the much more
disorganized aspect of the chalk. We hypothesize that part of the unanticipated order is inherited from
the foliated microstructure by means of, possibly, {0118} twinning. Growth line distribution suggests
that during chalk formation, the mantle separates from the previous shell several times faster than for
the foliated material. A shortage of structural material causes the chalk to become highly porous and
allows crystals to reorient at a high angle to the mantle surface, with which they continue to keep
contact. In conclusion, both materials are structurally similar and the differences in orientation and
aspect simply result from differences in growth conditions.