抄録
Apparently circular crystals of graphite prepared from carbon black were investigated by electron microscope. These crystals show circular growth patterns and produce spotty electron diffraction rings accompanied by ellipses and diffuse bands. Moreover, the circular crystal folded in half presents a fan-shaped appearance instead of a semi-circular form; i.e., two radii along the folded line makes an angle smaller than 180°.
These facts verify that the apparently circular crystal is really a stack of conical graphite sheets, each of which is successively rotated about the common axis in c-direction. It is pointed out that such a conical crystal can be formed by a spiral mechanism.
Laminar cleavage of conical crystals was observed, and the gliding mechanism connected with the spiral structure has been explained in terms of dislocations. From the spots distribution on the electron diffraction rings produced by some cleft sheets, the crystal has been concluded to be in the form of polygonal cone.
