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:
While my main interest is in opal and the opal towns, I still can't resist visiting some of the old gold mining towns as they share a similar kind of history. It never ceases to amaze me how seemingly intelligent men (and it was mainly men) would give up everything and undergo great tribulations to look for gold in some of the most desolate places on earth. Unfortunately, gold seems to have been formed in areas where weather conditions are extreme. The Yukon in Alaska and the deserts of Australia are striking examples and even areas in Victoria such as Ballarat and Bendigo are known for their extremes of weather.
Barbara and I love to travel in the outback. We don't go in for the arduous 4 wheel drive trips, crossing sand dunes and putting ourselves at risk, but we do love to head off and see where our travel takes us. In 2004 we set off up the Oodnadatta Track because it was somewhere we hadn't been before.We were driving a 1996 Toyota Hilux and towing an old off-road camper trailer. Having reached Coward Springs, an old railway station site on the original Ghan Rail line with a lovely hot artesian spring, we were told of a wonderful place to visit called the Painted Desert. So, after reaching Oodnadatta we set off for Painted Desert and were not disappointed as the colours of the hills were amazing with reds, whites and yellows abounding. As we were so close now, only about 200km, we, or maybe I should say, I, thought we should call in at Coober Pedy again as we hadn't been there for a while. This tends to happen a lot whenever we get close to an opal field. Barbara agreed and off we went.
If ever you travel through any of the opal towns it pays to stay awhile and talk to the locals. For some reason these places attract some of the real characters from all around the world. If you are looking to buy a small parcel of opal it gives you a reason to talk to the miners and they are often willing to tell you a little about themselves although not all of them will open up. We have been lucky to meet some of these characters on our numerous trips. One of the most interesting was Crocodile Harry.
Whenever you visit the opal fields there is much more to see than just opal mines and shops selling opal. There are all sorts of amazing and innovative machinery. There are all sorts of interesting buildings and there are other "things". This post includes pictures of machines, cars, buildings and "things" that we saw on our trip in 2012.
For all of us amateur opal cutters getting a regular supply of reasonable quality is one of the major problems. As opal mining slows down due to rising costs and lack of new finds, it is getting harder and harder to access.
I have been lucky living in Australia with relatively easy access to the opal fields, although it is a 2 day drive to get to the closest of them. In my twenties I went on a number of trips to Lightning Ridge and the Queensland boulder opal fields of Duck Creek and Yowah. I found many pieces of boulder opal and I still have some of them today. It was also possible to scour the opal dumps and pick up pieces of opal left by the early miners. It is extremely rare to find any today as most of the dumps at Lightning Ridge have been picked up and put through concrete mixing trucks fitted with sieves and all of the opal extracted. At Andamooka most of the dumps have been put through noodling machines with the same result.
No this is not a new opal field. It is, in fact an old gold mining area in north east Victoria.
Years ago Barbara and I visited the area to see the Eranundra Forest. This is an old growth area which has been heavily logged in the past but is still very beautiful with huge trees and marvellous tree ferns. Gold was discovered in 1855 in the Bendoc River with most alluvial gold being found in Chinaman's Creek, about 8km from Bendoc, and in the Delegate River. In 1857 the Morning Star mine was founded with ashaft sunk to 70 metres. Gold was mined from quartz at the rate of 2 oz per ton.
The term matrix opal refers to a type of opal where there is a base stone with tiny pieces of brilliant opal interspersed within this base stone. The base can be limestone, sandstone or even ironstone. At Andamooka and apparently nowhere else in the world, two types of matrix opal are found. One is called Andamooka Matrix and the other is now called Rainbow Opal Matrix.It used to be called "concrete" as this is exactly what it looks like. A limestone and sandstone matrix is found in Queensland and is called Boulder Opal.
In 2012, my wife Barbara and I went on a trip into central Australia to escape the wet and cold of Melbourne. As with most of our trips we tend to get diverted into at least one opal field. On this trip I was lucky enough to get to visit three of the fields namely, Coober Pedy, Mintabie and Andamooka. I have described the Mintabie trip on another Post so this one is about our Andamooka Opal Field trip. We have been here several times before and always enjoy the visit.
There are quite a few theories on how opal was formed and I will try and give a summary of the most popular theories in as simple language as I can. I am not a chemist, nor a geologist, so I may get some details wrong but I hope you get the gist of the process.
Opal is basically made from silica with a water content varying between 6% and 10%. For those chemists among you the formula is SiO2nH2O. Silica is a very common element and we know it as sand or quartz. The hardness of opal is between 5.5 and 6.5 on the Mohrs scale of hardness which makes it a relatively soft material to cut compared to saphires, topaz etc.