Biomineralization integrates complex processes leading to an extraordinary diversity of calcareous biomineral crystalline architectures, in intriguing contrast with the consistent presence of a sub-micrometric granular structure. Hence, gaining access to the crystalline architecture at the mesoscale, that is, over a few granules, is key to building realistic biomineralization scenarios. Here we provide the nanoscale spatial arrangement of the crystalline structure within the ‘single-crystalline’ prisms of the prismatic layer of a Pinctada margaritifera shell, exploiting three-dimensional X-ray Bragg ptychography microscopy. We reveal the details of the mesocrystalline organization, evidencing a crystalline coherence extending over a few granules. We additionally prove the existence of larger iso-oriented crystalline domains, slightly misoriented with respect to each other, around one unique rotation axis, and whose shapes are correlated with iso-strain domains. The highlighted mesocrystalline properties support recent biomineralization models involving partial fusion of oriented nanoparticle assembly and/or liquid droplet precursors.

中文翻译：

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揭示软体动物壳单晶棱镜中的晶畴

生物矿化集成了复杂的过程，从而导致钙质生物矿物质晶体结构的异常多样性，与亚微米级颗粒结构的持续存在形成了鲜明的对比。因此，获得中等规模（即几个颗粒）的晶体结构是建立现实的生物矿化方案的关键。在这里，我们提供了Pinctada margaritifera棱柱层的“单晶”棱柱内的晶体结构的纳米级空间排列外壳，利用三维X射线布拉格布拉格式分型术显微镜。我们揭示了中晶组织的细节，证明了晶体的凝聚力延伸到了几个颗粒上。我们还证明了存在较大的等取向晶域，它们围绕一个唯一的旋转轴彼此之间略有错位，并且其形状与等应变晶域相关。突出的介晶性质支持最近的生物矿化模型，该模型涉及定向纳米粒子组件和/或液滴前体的部分融合。