10 “How to Cut & Polish” Opal Guide
You may think that opals come just as pristine and ready to be placed into a setting, as you see them when they are actually ‘in place’. You would not be alone, as many opal loving people seem to forget that there is much work to be done, before the gemstone can be placed into that ring setting, or embraced into a fine, artistically-created opal necklace.
In this guide for learning how to cut and polish opal parcels, you will be introduced to the wonderful world of opal gleaning, and then you will see just how many steps there are to ending up with a beautiful opal stone.
The first step in making a gemstone really stand out and be of great value is to dig up a ton of dirt and rock and ‘fish out’ the opals. Instead of going through all of that rough and ready opal mining, most people, in the opal business, choose to purchase their raw opals directly from the opal miners. These rocks are rough and have not been touched except for the actual mining process.
Once the unfinished opals are collected in mass enough to take to market for sale, these early opals are then sold by the miners, to the secondary wave of gemstone artisans. Unfinished opals from Australia are known and referred to as ‘parcels’ as these are bulk quantities of opal are in their roughest and most durable states.
Potential opal buyers sort through the parcels and attempt to predict the value of stones, which can be produced, from the rough material. Even though it may sound like fun, in actuality, opal cutting and polishing is a very specialized skill. Rough opal is not easy to deal with and with each step in the cutting process, the opal stones become less malleable and forgiving. The skilled master-cutters and polishers of opals, take great pride and caution when dealing with such a truly magnificent piece of gemstone wonderment.
However, there is never at all any guarantee of a fine opal cutting and polishing, as opal cutting can produce very unpredictable returns. Once the opal cutter has sorted through the parcel and decided which pieces are worth his or her ‘cutting’ time and patience, a diamond saw is used to cut the rough opal into ‘ rubs’ (opal in the rough shape of a stone). During this slicing process, any excess material, cracks and potch, which is colourless opal, is cut off, and the piece of opal is cut into a basic stone shape.
Once the opal stone has been made, as close to what is desired by the cutter as possible, it is now time to minimize waste and maximize the end size of the stone. The ‘Golden Rule’ for any good stonecutter worth his weight in salt, is that the opal needs to be kept as large as possible. Each moment of cutting thusly reduces the size of the stone, so control must be exercised at all times. The second working rule is that opal can be ‘burned’ or may even crack if subjected to extreme temperatures. For this reason, warm, clean water must always be used when cutting opal to avoid overheating due to friction. ‘Burning’ a stone during polishing results in small pits that form on the surface of the stone thereby ruining the smooth surface and polish.
After the opal stone has been cut on the saw by hand, the opal cutter will then normally place the stones on ‘dop sticks’, consisting of nails or lengths of wood dowling, using heated wax to adhere the stone to the end of the stick. This permits a greater degree of control of the stone, on the cutting wheel, especially when the stone is quite small. The hard wax is softened on a burner to permit the fixing of the stone, which is first adhered with the face of the stone pointing upwards. The face of the stone is decided by the opal cutter, considering which side has the best colour, and the best shape for the stone.
The opal cutter then utilizes a series of diamond grinding wheels, in order to shape and perfect the stone. Importance is placed on removing imperfections in the stone, such as sand spots, and removing saw marks and rough spots from previous stages. The face of the stone is shaped into a cabochon, which is a dome shape, and the final shape is decided depending on the stone. Again, maximising the size of the stone is an important consideration.
Last but not least, in the steps for cutting an opal stone is that of the polishing task. The face of the stone is the only location that is polished and Serium Oxide is used as a polishing agent on a felt wheel with water, to give the stone a beautiful polished look. If the cutter is happy with the shape, and the absence of scratches, grinding marks or imperfections, he then carefully removes the stone and places it back on the wax, with the back facing up.
With any luck, as well as a masterful polisher, the stone os now a spectacular, shining opal ready to be placed into a setting or left ‘as is’ for a valuable investment.