Make your own bezel to hang a gemstone cabochon, or flat-back, from a necklace. There are several different ways to make a bezel, but one of the easiest techniques is the wire wrap bezel. With the right kinds of wires and tools and by following a specific procedure, you can make a bezel that fits your gemstone cabochon. Use the colour of metal jewellery wire that matches the metal of your necklace so that it looks like you bought it that way.
Measure the circumference of the gemstone cabochon with measuring tape and add 2 inches to this length. Cut five pieces of half-hard 1mm wide flat wire with wire cutters and place them next to each other with the ends aligned.
Cut a piece of beading wire in the same colour metal to 2 inches long. Wrap the beading wire around the middle of the group of flat wires to bind them together, and make sure they lie next to each without overlapping. Wrap two more 2-inch pieces of beading wire around the flat wires, halfway from each edge toward the middle.
Bend the group of flat wires around a round form, such as a ring mandrel to get it into a basic round shape to fit around the outside of the cabochon. Bend the two wires on the outside edge of the group on either side of the wraps you made with the beading wire -- these bends will hold the cabochon in place.
Place the cabochon in the wire bezel and press it against the outside edge all the way around. Bend the ends together with a pair of chain nose pliers where they meet at the top of the cabochon. Wrap the ends together tightly with a 4-inch length of beading wire to secure the top of the bezel.
Wrap the ends of the wires extending from the top of the bezel around a round nose pliers to form a loop. This is the loop you will use to hang the gemstone cabochon from a necklace. Wrap the ends around the base of the loop twice and snip the excess ends of the wire with a pair of flush cutters.