A diamond sawing process, in which guidelines on the outer surface of a rough diamond are used for the sawing of up to six pyramid shapes (340) as fragments from a particular piece of tetrahedron shaped (sawable) diamond, whereby the maximum weight of a polished round brilliant cut (or other round cut diamond) is obtained from a particular rough diamond, together with the fragments. A marking pen or equivalent is held parallel to the centre line of the diamond (300), and adjusted so that its point (330) touches the shortest side of the diamond; when the diamond is rotated relative to the point, a circle is marked which represents the maximum round diameter that can be cut for that diamond. The pen crosses the ridges (412, 414, 416, 418) of the diamond, and these crossing points define the starting point of sawing. In a further refinement, the marker pen and its point can also be used to mark the maximum height of the fashioned diamond, these marks being placed on the ridges, and a pyramid shape cut from one or both of the top and bottom (culet) of the rough diamond. Preferably, a laser can be used both to mark and saw the diamond in one operation, thereby saving time and the possible need for readjustment or resetting of the diamond on its fixing. |