Crystals (Oct 2017)

Formation Mechanism of CaCO3 Spherulites in the Myostracum Layer of Limpet Shells

  • Shitao Wu,
  • Chang-Yang Chiang,
  • Wuzong Zhou

DOI
https://doi.org/10.3390/cryst7100319
Journal volume & issue
Vol. 7, no. 10
p. 319

Abstract

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CaCO3 spherulites were found in the myostracum layer of common limpet shells collected from East Sands, St Andrews, Scotland. Their microstructures were revealed by using powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray microanalysis. The formation mechanisms of these spherulites and their morphology evolution were postulated. It was proposed that spherical particles of an inorganic and biological composite formed first. In the centre of each spherical particle a double-layer disk of vaterite crystal sandwiching a biological sheet developed. The disk crystal supplies a relatively strong mirror symmetric dipole field, guiding the orientations of the nanocrystallites and the arrangement of mesorods and, therefore, determining the final morphology of the spherulite.

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