The surfaces of the melt grown doped KMgF3 crystals, grown by czochralski pulling technique with 5% doping of NiF2, were investigated using an optical microscope The crystals exhibit striations of type-I and type-II. From the topography of matched cleavages, it is demonstrated that these crystals exhibit perfect cleavages along (1 0 0) planes. The results of etching of (1 0 0) cleavages at different concentrations of the etchant are reported. Ten percent H2SO4 is shown to be the most suitable concentration for delineating dislocations intersecting (1 0 0) planes of these crystals. The shape of the etch pits is dependent on concentration of the etchant. Hundred percent H2SO4 produces circular, whereas lower concentrations produce square etch pits. Besides isolated dislocations, low angle grain boundaries and helical dislocations are shown to exist. Variations of lateral, vertical and areal etch rates with etchant. concentrations of the etchant are graphically analysed.