Opal cutting using flat lap machines has many advantages. For many years I had cut and polished opal using the conventional grinding wheels. I started on a two wheel carborundum grinder as that was all I could afford. By being very careful and ensuring I used the full width of the wheel this produced reasonable results. I was then lucky to purchase a four diamond wheel grinding machine together with a home made polishing disc run off an old washing machine motor. I still use both of these items of equipment today and they work well. Photos of these two pieces of equipment are shown below.
If you have any thin pieces of opal with nice colour but believe it is too thin to cut a cabechon then think about making a doublet.
A doublet is basically a fairly thin layer of usually opal glued to a thicker layer of opal potch or some other material to make a stronger stone. A cabechon is then cut from the prepared material. Don't be afraid to have a go at making doublets. It is not too hard and you don't need a lot of equipment. The equipment you will need, in addition to opal cutting equipment is as follows:
Cutting Opal is really about grinding away the colourless opal or potch and shaping your stone to an appealing shape while revealing the best colour on the prominant face of the stone.
As explained elsewhere great care should be taken to study the stone before any grinding is carried out. Look at the stone from all angles under a good incandescent light or sunlight and work out which face has the brightest colour. Study the stone with and without using your 10 magnification loupe so you can see any surface irregularities , sand or cracks which will have to be removed before polishing.The face of the stone with the brightest colour should be the top of your finished stone. Mark this with texta colour and then proceed to dop your stone with the wax being on the opposite side to the selected top. (See the post on Dopping Opal on this page) You may need to grind away any sand or loose material on the back of the stone to ensure the wax will get a grip.
What on earth does "dopping opal" mean?
If you have ever tried cutting and polishing opal or any other small stone by holding it in your fingers you will know it is very difficult to do and will often result in grinding a hole in your finger as well as ruining the stone.
The solution is to glue the opal onto the end of a small stick or nail. You will then have much better control of the cutting process and it is much safer.
The cutting and polishing of opal will require some machinery in order to shape and polish the stones. There are many different types of machinery available and it can be very expensive. If you are just starting to cut opal or any other gemstone, you can do so without spending a lot of money. This post will describe probably the minimum amount of equipment you will need to start with. As you get more confident you can then experiment and upgrade to better quality equipment. With the equipment I will describe you will be able to cut and polish beautiful stones: you may just have to be a bit more careful than if you had the more upmarket equipment.