Hobbies And Interests
Trim Saw
An opal cutter uses the trim saw to cut the rough opal into pre-gem shapes called "rubs." The shapes are determined by the individual stone. The cutter takes care to save as much of the rough stone as possible, only eliminating the colorless part of the opal, known as the "potch," and any parts that are cracked or fractured. The trim saw has a circular, diamond tipped blade that cuts through the opal while water is poured on the stone to keep it cool. Most opals are cut into cabochons, which are gems that are dome shaped on one side and flat on the other. This cut brings out the most color in the opals and increases the illusion of depth.
Dop Sticks
After the opal has been shaped, the rub is mounted on a dop stick. This could be a wooden dowel or even a large nail. Dop sticks give the gem cutter something to hold on to and afford better control over the movements of the stone. They also keep his fingers away from the spinning wheels of the grinder and the polisher. The opal is secured to the dop stick with melted wax. The cutter decides which side of the stone has the best color and mounts this side face-up. The wax on the mounted stones must be thoroughly cool before the stones can be polished. Some cutters prefer that the dop sticks sit overnight.
Grinding Wheels
The cutter then takes the mounted stone and holds it against a series of rotating grinding wheels. Some machines have vertically mounted wheels and look like the machines used to make keys. Others have horizontal grinding wheels and rotate like an old record player. These wheels are covered with diamond grits, coarse to fine. Starting with the coarse, all the imperfections are ground off the stone and the stone is shaped into the familiar dome of a cabochon. Water is used to keep the stone from overheating during the grinding process.
Polishing Wheels
After the stones have been shaped and smoothed, they are taken to the polishing wheel, which made of felt. Serium oxide is a common polishing agent which is used with plenty of water to keep the stone cool. The polishing wheel will bring out the fiery colors in the opal but also any missed imperfections such as scratches or grinding marks. Sometimes the cutter must take the stone back to the grinding wheel for further work. Once the stone is polished, it is removed from the dop stick and reattached with the back side up. The process of grinding and polishing is repeated, except that the back of the stone will be flat, rather than domed. This is also when the "girdle," or edge of the stone, is ground and polished. The girdle insures a secure fit when a jeweler mounts the stone in a setting.