A method of separating a sheet of a brittle material into portions by means of laser-scribing, comprising steps of: (a) providing a sheet of a brittle material having first and second opposing major surfaces separated by a thicknesst; (b) providing a source of laser energy adjacent said first surface, adapted for supplying a focussed beam of laser energy converging to a focal spot in a plane parallel to the first surface; (c) irradiating the sheet of brittle material with the focussed beam of laser energy, the plane of the focal spot of the beam initially being positioned within the sheet just below the first surface; and (d) continuing irradiating while simultaneously providing relative movement between the focal spot of the laser beam and the sheet to move the focal spot at a pre-selected rate and path extending over the first surface, and moving the depth of the plane of the focal spot at a pre-selected rate through a major portion of thickness t of the sheet to form a micro-crack zone extending along the pre-selected path from just below the first surface to a shallow depth just below the second surface.