几种生物CaCO_3霰石结晶的取向性

ＣａＣＯ３结晶广泛分布于生物界，其主要结晶形式为方解石、霰石及球霰石。用Ｘ－射线衍射法对三角帆蚌及合浦珍珠母贝的珍珠层、墨鱼骨和大黄鱼耳石的ＣａＣＯ３结晶进行测定，发现各样品均有一定取向性，以三角帆蚌和合浦珍珠母贝珍珠层的取向性为最强，墨鱼骨的取向性次之，大黄鱼耳石的取向性最小，以上材料粉末样的衍射分析表明，各样品对应ｄ值间差异极小，均为Ｘ射线衍射卡（５—０４５３）所表征的ＣａＣＯ３霰石结构。

THE ORIENTATION OF CaCO_3 ARAGONITE CRYSTALS FROM SEVERAL ORGANISMS

The CaCO3 crystals are widely distributed in organisms. The calcite, aragonite and vaterite are the main crystal polymorphisms of CaCO3. In this paper, CaCO3 crystals were obtained from the nacreous layers of Hyriopsis cumingii Lea and Pinctada martensii Dunker, the internal shell of a cuttlefish and the otolith of Pseudosciaena crocea. X-ray diffraction measurement was used to analyze the crystal orientation of CaCO3 crystals: The results showed that each kind of natural CaCO3 crystal has an orientation on specific plane. In detail, the crystal orientations of the nacreous layers are higher than the internal shell, and the orientation of the otolith is the lowest. Except the nacreous layers of Pinctada martensii, whose highest peak is on the crystal plane (312), all the other three natural samples have the highest peak on the crystal plane (012). As to ground CaCO3 crystals, the differences between their corresponding d values are very small, so each ground Sample has the CaCO3 aragonite structure characterized by the JCPDS card (5-0453).