Andamooka matrix opal is basically a limestone base rock impregnated with tiny pieces of precious opal. Because the limestone is very pale it is often difficult to see the play of opal colour in the stone and hence a method of darkening the limestone background was developed so the colour of the opal could be seen.
The treatment described here in no way alters the opal component of the stone. It merely allows it to be seen with the naked eye. It is amazing how the stone can be transformed from a pale stone with seemingly little colour to a dazzlingly brilliant black opal. Purists will often oppose such treatment but if it can bring out the unseen beauty in a piece of opal I can see no reason not to do it. It also allows those of us who cannot afford good quality opal, the chance to cut brilliantly coloured stone at a very low cost as matrix opal is so much cheaper.
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.
The photograph below is of the White Dam Opal field.
In July 2007, my wife Barbara and I visited Andamooka. We camped in the Andamooka Caravan Park which is on the main road into Andamooka township.
Andamooka is a small town but still has 2 hotels, a supermarket, bottle shop, Post Office, motel, and various places to buy opal.