Andamooka Rainbow Matrix Opal is fast becoming popular with those who can't afford a "Real Opal".
Originally it was called "concrete" because that was what it looked like although you could see small specks of opal in amongst the concrete like grains. It is a porous quartzite host rock in which opal has been deposited amongst the quartz grains. In its raw state you can hardly see the opal and for this reason the early miners discarded it as valueless. If you hunt around the mullock heaps or even on the roadsides in Andamooka you still have a chance of picking up a piece. A photo of a typical piece of concrete is shown below.
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.
Cooper Pedy has just celebrated 100 years since it was founded as an opal field. Opal was found at what is now called Coober Pedy by 14 year old Willie Hutchison. He had been out prospecting for gold with his father and two other prospectors in January 2014. His father asked him to stay in camp while he and his two companions went looking for water. Willie disobeyed and set off on his own and as well as finding water he found opal and this soon led to the establishment of the Coober Pedy opal field. Read more about this in my post called Coober Pedy Opal Field Original discovery of opal.
As with many of our trips to the opal fields we did not really intend to go there. We set off to escape Melbourne's winter with our destination as Wooli, near Grafton, on the New South Wales coast. We took the kayaks and the fishing equipment and actually settled in for three weeks of active recreation. Unfortunately the weather turned and we were faced with heavy rain and strong winds which affected the fishing and restricted the kayaking to some extent. We stoically sat it out for the three weeks during which we had a few day trips to Ballina and Coffs Harbour. At Coffs Harbour we visited the Opal Shop located about 500 metres north of the Big Banana on the Pacific Highway. We only dropped in for a visit because the weather was bad and we had to fill in a bit of time. There was a lovely display of opal there and we had a chance to talk to the owner about opal. She and her husband had a mine at Lightning Ridge some time back and had spent many years mining for opal. There were photographs of their mine in the shop and she was very informative. It is well worth a visit.
There are many interesting things to see and people to meet at Lightning Ridge and indeed at any of the opal fields. These towns are unique and have attracted a great diversity of characters. I don't think we have visited any of the opal towns without meeting people with a different outlook on life. People obviously move to these places to escape the mundanity of life in the cities. Certainly out here you can pursue any lifestyle you want. You can build a castle, you can become a recluse, you can paint, build sculptures, write poetry or even mine for opal. It is all here to inspire you.
The last time we visited Amigo's Castle was in the 1990's. Amigo was still constructing it with no finish date in sight. He also didn't like visitors at that time so Barbara was lucky to be invited in to take some photographs, and to meet Amigo. You can read about that visit and see photo's in my earlier post on Amigo's Castle on this web site.
During the last month I was contacted by Andre who told me he had a couple of pieces of Andamooka matrix opal he had collected some time ago. He purchased one of these from Cash Converters and they were part of a deceased estate. Andre was obviously quite astute as the Andamooka matrix opal was not treated. Unless you know what you are looking for, some untreated Andamooka matrix opal can be quite un-exciting (if there is such a word). It is usually very pale with only a hint of colour in it. However if it is treated by heating it in a sugar solution for several hours and in a sulphuric acid solution the background turns black as the acid combines with the sugar in the pores of the stone to form carbon. This change of background allows the opal colours to really stand out. It is a really amazing transformation and the end result can be a gemstone of great beauty. Andre treated the Andamooka matrix opal with sugar and battery acid. Most people insist you need 98% sulphuric acid but these results show that this is not necessarily the case always although Andre now advises that the battery acid started boiling in his wall oven and in the end it was destroyed. Might be better to stick with the 98% acid and cook it in a well ventilated area. I use an old electric fry-pan and a pyrex dish and this works well.
Opal is a form of silica which has water molecules attached to it (varying from 3% to 21%) and is called hydrated silica. It is an amorphous material, which means that it does not have a crystalline structure. It's internal molecular structure can be ordered. Opal consists at a micro level of a 3 dimensional grid of minute silica spheres each separated by voids. These are very small and can be arranged in a regular hexagonal or cubic close packed lattice or they can be arranged in a random pattern. If they are arranged in a regular pattern the opal formed is called "precious opal" and will display various colours when light is diffracted by these spheres particles. The size and spacing of these silica spheres will determine the colours shown by the opal. If the array of spheres is random then there will be no display of colour and the opal material is called common opal.
On this website I have written a few blogs on the life of Minnie Berrington, the first woman opal miner at Andamooka. I was fortunate a month or so ago to hear from relatives of Minnie who had read the posts.
Both Peter Berrington and his daughter Stephanie contacted me by email. They couldn't give me very much information but did give me little which I will now share. Some of it will be a direct copy from Peter's email.
The men who work in the opal fields are a hardy lot. The work is extremely hard and the weather conditions are deplorable for much of the time. They are often forced to live in primitive shelters and with few of the modern comforts that we have today. You would not think they would have a lot to laugh about except when they found some opal. But that is not the case. Maybe the heat affects some of them, maybe some are just mad by nature but that does not stop them from creating strange creations and signs out there in the opal fields.