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.
We have driven on the Stuart Highway many times but have always sailed past the turn off to Mintabie just a few kilometres past Marla. This time we were determined to visit Mintabie as it is only about 35 km off the Stuart Highway.
We camped at the Marla Road Station Caravan Park, which by the way, is a lovely grassed park with all amenities including power. Leaving our van here we set off quite early to Mintabie. The road in was a little corrugated but easily accessible in the dry by most vehicles.
In 1926, Minnie Berrington, a young typist from London arrived at Coober Pedy becoming one of only 3 women on that opal field at that time. Conditions may not look all that good at Coober Pedy today but at that time they would have been much worse.
Access to the town, if you could call it a town then, was appalling. The road from Port Augusta was unmade and was really just a dirt track. Supplies were difficult to obtain and the weather was extremely hot in summer with little shelter and certainly none of the "mod cons" we have today such as airconditioning and refrigeration. Food and water was even difficult to come by. This did not deter her and for a while she was employed to look after Jacob Santings store at Coober pedy.
In the early 1930's there were a few miners working at Andamooka. One of these miners was an old European who lived in an old dugout away from the main centre. He was regularly seen walking across the hill to collect water from the well in the main centre, but he rarely spoke to anyone. At that time there was a tin store near where the school is now, run by Reg Absalom. During a long heatwave it was realised that no-one had seen this miner for several days, which was quite unusual. Reg went looking for him and found him dead on the hill. He'd been dead for about three days. The decision was made to bury him where they found him, and this was the start of the original cemetery.
In my teens I had a strong interest in fossicking for gemstones. This led to gold panning and gemstone fossicking trips to Beechworth, Walhalla and other similar places,
In 1966 my cousin Ken and I decided we should try and find some opal as we had read about its beauty and the possibility of finding chips and small pieces rejected or missed by the miners at some of the older fields. After some study we settled on an old field called "Pride of the Hills" situated in Queensland west of Cunamulla and east of Toompine. We had no idea of what to expect but headed off in my Cortina sedan in September of that year. We took plenty of fuel, water and food to last the two weeks as well as picks, shovels and sieves.