Crystal orientation in the shell of the domestic fowl: an electron diffraction study.

The eggshell of the domestic fowl has been studied by transmission electron microscopy and diffraction. Thin sections of shell were prepared by chemical and ion-beam thinning techniques. Each calcite column of the palisade layer consisted of crystallites of diameter 20 to 30 micrometer with some tendency for crystallite alignment within a single column. Evidence indicates that there was no significant preferred orientation in the palisade layer as a whole. Only in the surface layer was any preferred orientation detected, and here (1014) planes tended to lie parallel to the surface. The results are compared with previously published data, and calcite nucleation and growth are discussed.