How to Cut Onyx Backsplashes

Hold the backsplash against the wall, in the position in which it will be fixed. Identify the places where cuts need to be made, such as around wall-mounted faucets, light fittings or electrical outlets. Use a pencil to mark cut lines that can be transferred directly onto the backsplash while it is in position, such as the position of faucets along the base. Draw lightly around the outer edges of the backsplash and remove it from the wall. Use a tape measure to determine the positions of other cuts relative to the outline of the backsplash drawn on the wall. Record the measurements.

Use a soft pencil to transfer the cutting lines, measured on the outline drawn on the wall, to the top surface of the backsplash. Do not proceed until you are certain that the lines are in the correct positions. Once cut, you cannot easily rejoin pieces of onyx marble.

Use an electric drill fitted with a thin masonry bit to drill a hole at each corner if you intend to cut lines that form angles. The small holes you drill will give you clearance to change the angle of the jigsaw blade, creating a curved corner that resists fracturing and helps prevent crack lines. Unplug the drill, if necessary, insert the bit into the center of the drill chuck and tighten it with the chuck key. Remove the key from the chuck before restoring the power supply. Test the drill to make certain that the bit is located centrally and does not wobble or spin out of true.

Don safety goggles. Hold the drill vertically, with the masonry bit positioned slightly inside the line being cut, so the hole will be entirely within the area being removed. Squeeze the drill trigger and let the bit cut into the onyx marble. Don't try to force the drill through the stone - this may cause the underside of the stone to "pop," leaving a small and undesirable crater on the surface.

Fit a fine-tooth plywood blade or a coarse-tooth metal-cutting blade to the jigsaw. Attachment methods vary according to the make and model of your saw but usually consist of a small clamp into which the top end of the blade is inserted. The blade is secured or released by tightening or loosening a blade locking screw.

Rest the jigsaw soleplate on the onyx marble's surface, the blade aligned with the start of the first cutting line. Switch on the saw and very gently ease the blade up against the edge of the onyx marble. Apply slight forward pressure to push the blade into the material. Continue to gently push and guide the blade along the line.

Finish the cut with extreme care. The final fraction of an inch is liable to crack if under any pressure, so ease the blade forward as gently as you can.