Amigo's Castle at Lightning Ridge Opal Field

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.

More Andamooka Matrix Opal

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.

The opal field towns were established at a time when building materials were very scarce and hence the early architects had to very inventive and had to recycle almost everything they could find. The first miners arrived on foot or by horse, or in the case of Andamooka, by primitive motor vehicle, and hence could not bring anything other than the very basics with them. The shelters they created were made with mud, boughs of local trees and if they were lucky, some bits of canvas and tin. While these were primitive they did provide some sort of shelter from some of the extremes of weather faced in the opal fields. While most were very basic there are some fine examples of Architecture in the opal fields.

As you travel around any of the opal fields, particularly Andamooka, Coober Pedy and Mintabie. you will find a proliferation of old abandoned vehicles. Miners have obviously purchased these at some time to use on the opal fields and when they have become un-repairable they have been left to rot. While these relics might be unsightly in some places it adds interest to the opal fields.

Most of us who visit the opal fields do not have the expertise or knowledge to actually mine for opal. A lot of us though, do have a desire to find a piece of opal. There is a way that this desire can become reality, and that is by noodling and specking for opals. Noodling is sifting through the dumps left by the miners and specking is walking slowly along staring at the ground looking for any signs of colour.

One of the major impediments to the establishment of any of Australia's opal fields was the lack of available water for the miners and their animals. The opal fields are located in areas which were once a vast inland sea which had later turned into desert. The opal was formed at the base of a varying depth of sandstone deposited over millions of years. Opal was only found when due to upheavals and weathering of these sandstone layers, pieces of opal (floaters) broke away from the opal level and were left on the surface.

Lightning Ridge is located in New South Wales, north of the township of Walgett and south of the Queensland border. It is renowned as the largest known deposit of black opal in the world. Black opal is found in much smaller amounts at a number of other localities such as Andamooka and Mintabie, but it is acknowledged that the quantity and quality of the Lightning Ridge black opal is unsurpassed.