Freshly cleaved (100) cleavages of KBr single crystals grown in the laboratory have been etched in an etchant containing 10 ml absolute ethyl alcohol, 0·5 ml n-butyl alcohol, 0·1 ml formaldehyde and 0·1 ml distilled water. Both clockwise and anticlockwise spiral etch pits are produced. By etching (100) matched cleavage pairs in the same conditions, one-to-one correspondence in number, position and shape but not the sense of some of the spirals has been established. By re-etching a cleavage face having spiral etch pits in dislocation etchant, an etch pit is formed exactly at the centre of each spiral, indicating thereby that the spiral etch pits nucleate at the sites of dislocations terminating on the crystal face. The implications are discussed.

Transparent single crystals of KBr with cubo-octahedral habit have been grown from aqueous solution containing PbI2 as an impurity. On cube faces of these crystals, square-shaped hillocks with growth layers in the <100> direction have been observed; while on octahedral faces, strictly crystallographically oriented triangular hillocks and cone-shaped hillocks have been observed. Occasionally, growth spirals on octahedral as well as on cube faces have also been observed. It is shown that the cone-shaped hillocks on (111) faces are nucleated at the sites of dislocations, whereas the triangular hillocks have nothing to do with dislocations. The implications are discussed.

The growth striations revealed by etching (100) cleavages of cubo-octahedral transparent KBr(PbI2) crystals grown from solution by the evaporation method are described and discussed. The formation of these striations is attributed to fluctuations in temperature during crystal growth. It is shown that at first the crystals grow with an octahedral habit by the deposition of layers on (111) faces and that at a later stage cubic faces also develop. The implications are discussed.