Special vaterite found in freshwater lackluster pearls

In recent years, scientists have special interests in biovaterite found in freshwater cultured lackluster pearls in south China. Vaterite is an unstable crystalline form of calcium carbonate and rare in nature. In this work, we first reported that vaterite crystals in freshwater lackluster pearls have a similar hiberarchy to that of nacre with the "brick and mortar" structure. The dimension of a single vaterite tablet is approximate 8 x 2 x 0.4 mu m(3). In half-lackluster pearls, the aragonite-vaterite interface is abrupt, and the boundary is sequential; two different kinds of contact modes between aragonite and vaterite tablets were observed. Furthermore, crystallographic orientation regulation of vaterite tablets was analyzed for the first time. The results show that vaterite tablets are arrayed with the [010] direction perpendicular to the tablet plane; strong [010] texture and relatively weak [101] and [102] texture were obtained in a region from several neighboring tablets to micrometer scale. In addition, the misorientation angles between adjacent tablets mainly concentrate on small angles lower than 10 degrees and have another gather in 60 degrees.

近年来，科学家们对在中国南方淡水养殖的无光珍珠中发现的生物球霰石特别感兴趣。球霰石是碳酸钙的一种不稳定晶型，在自然界中较为罕见。在这项工作中，我们首次报道淡水无光珍珠中的球霰石晶体具有与珍珠层相似的层级结构，即“砖泥”结构。单个球霰石片的尺寸约为8×2×0.4μm³。在半无光珍珠中，文石 - 球霰石界面明显，边界连续；观察到文石片和球霰石片之间两种不同的接触方式。此外，首次对球霰石片的晶体取向规律进行了分析。结果表明，球霰石片以[010]方向垂直于片平面排列；在从几个相邻片到微米尺度的区域内，获得了较强的[010]织构以及相对较弱的[101]和[102]织构。此外，相邻片之间的取向差角主要集中在小于10度的小角度，并且在60度处还有另一个聚集。