抄録
When the melt of KCl is rapidly cooled in a crucible it is known that a single crystal naturally cleaves into fragments with various edges. Based on experiments performed by the present authors the following observations in relation to this cleavage are discussed: (i) Mechanical defect structures such as step lines and caves are observed in white light and photoelastic patterns appear in polarised light. (ii) Optical defect structures which are giant clusters of optical defects are observed in monochromatic light. (iii) Both defect structures are of microscopic scale and frequently distributed on certain definite planes such as {100}, {110}, and so on.
It is concluded that the natural cleavage of a KCl crystal must be preceded by the above defect structures which are induced during the crystal growth.
