Main conclusions of this work are drawn as follows : 1 ) in nacre of hyriopsis cumingii ( lea ) shell , the aragonite crystallites exist two kinds of orientation , one . which is generally accepted , is the c axis of aragonite perpendicular to nacreous layers , the second , which is proposed in this paper , is the [ 012 ] axis of aragonite perpendicular to nacreous layers 本文所获得的主要成果有： 1 )明确提出三角帆蚌珍珠层中文石晶体的择优取向除了存在公认的其c轴垂直珍珠层面外，还存在其[ 012 ]轴垂直珍珠层面的新取向。
In this paper , the nacre of hyriopsis cumingii ( lea ) which is one of the main freshwater pearl - forming mollusk in china is studied emphatically , as compared with the nacre of three species of saltwater pearl - forming mollusks , pinctada martensii ( dunker ) , pinctada maxima ( jameson , and peteria penguin ( roding ) . the basic characteristics of nacreous and prismatic layers are understood by powder x - ray diffraction analysis , trace elements analysis , amino acid composition of protein and differential thermal analysis 本文以我国主要育珠蚌淡水三角帆蚌贝壳珍珠层为重点研究对象，以三种海水育珠贝马氏珍珠贝、企鹅珍珠贝及大珠母贝贝壳珍珠层为对比研究对象，首先通过粉末x -射线衍射、微量元素分析、蛋白质氨基酸分析及差热分析对珍珠层及其与之密切共生的棱柱层的基本特征进行了初步研究。
