Whenever we think of opal we usually think of gems used in jewellery, but there are some opals and other gemstones which portray beautiful and intriguing patterns, but which are not necessarily suitable for use as jewellery.
Some of the stones shown below are from my collection and while not the most valuable, they are still amazing for the patterns and colours they exhibit.
Lightning Ridge is famous for its "black opal" but it also has its share of strange buildings. The strangest of all has to be the "Universe Observatory" or "Astronomer's Castle" built by Polish Alex Szperlak.
There are many amazing sights around Lightning Ridge, but few better than Amigo's Castle.
Vittorio Stefanato, known locally as "Amigo", opal miner and castle builder, started his project in 1985 when he started getting tired of opal mining. Initially he sourced his stone from his mining lease but soon had to travel to all areas around Lightning Ridge as his castle grew in size.
Opal at Andamooka is found in a narrow band of depths varying up to 600 mm. In this bed there are many boulders of strongly bonded quartzite of varying sizes.,Today, as you wander among the great piles of disturbed overburden which is mixed with the old opal level , you will come across many of these boulders. They are extremely hard and difficult to break.
The opal fields of Australia were formed at the bottom of a large inland sea. In this sea there were all sorts of marine creatures including turtles, crocodiles, dinosaurs, all sorts of fish and of course shellfish. As these creatures died their bodies sank to the bottom of the sea and were covered with sand and silt. Over millions of years the sea dried up and various clays and sand were deposited over the sea bed. The bodies of the sea creatures obviously rotted away and the bones and shells, being made of calcium carbonate, were dissolved by acids in the soils. This would have left cavities in the shape of the dissolved creatures. Silica then seeped through fissures and cracks and filled these cavities which acted as casts for the silica that filled them. In some cases the silica turned into opal and the reult was opal in the exact shape of the shell or bone that had been deposited on the sea bed so long ago.
It was all very good finding opal in the early days but if no-one wanted to buy it, then there was little use risking your life trying to find it. Still this did not deter the brave souls who ventured into the harsh environment of central Australia to chase opal. In the 1880's opal had been found in Queensland and miners had established themselves in various areas where opal had been found. At that time they realised they had found a valuable and rare gem but there was no-one to buy it. Miners would hoard the best quality opal and throw away the more inferior material. There are records of miners with sugar bags full of top quality opal but it was of no use to them in outback Queensland.
Yowah is a small town in south west Queensland and is famous for the Yowah Nut which is only found here and nowhere else. The yowah nut is a relatively small, hollow ironstone concretion in the shape of a nut. They occur in closely packed horizontal layers with sandstone overlaying these beds of nuts. In some cases the centre can be filled with gem quality opal but in most cases they are filled with air, powder or some other non valuable material. Yowah also has some really beautiful matrix opal which is the same ironstone concretion often with small flecks of precious opal interspersed through the ironstone.See my post on Yowah Nuts post for more details.
White Cliffs is famous in Australia as an Opal Town but it is also unique for another reason. It was the site for world's first experimental solar station for supplying power to small outback towns.
In 1979 New South Wales was experiencing major political problems. Premier Wran believed that a major environmental project for the state would improve his party's popularity and he had in mind a likely project. The oil crisis in the 1970's had everyone talking about alternative fuel sources so the time was ripe for a solar energy trial.
Yowah is a small outback opal town in Queensland located about 1,000 km west of Brisbane and about 130 km west of Cunnamulla.There is a sealed road all the way so it is very easily accessible. The opal field surrounding Yowah is quite small, being about 4 square kilometres. It has all the amenities you need for a fossicking holiday. There is a store, cafe and two camping grounds. (one where you have to pay fees and a free campground with showers and toilets but you have to pay for the showers). The paying campground has a bathhouse attached where you can loll in your bathtub sipping a glass of champagne looking up at the sky. The only downside is that the tubs are filled with hot artesian water straight from the bore and it does have a maloderous smell. That is it stinks of sulphur. But apart from that it is a great experience and well worth it after a day of dusty fossicking.
It seems that the discovery of opal in Australia was often due to chance with many of the discoverers either looking for something else or drilling for water in the outback. When we understand how opal was formed it is not a surprise. Most opal is buried deep beneath the earth and it is only possible to find it on the surface if the earth has been weathered by wind and rain to a level below the opal layer. When this occurs pieces of opal can become exposed. These are called floaters as they also can be washed away by the elements and can end up a long way from where they were originally formed. Finding of these floaters often led to the discovery of a field. If erosion has not reached the opal level there is no way of knowing if opal exists unless a hole is bored. This is expensive and very much a hit and miss method as opal is often scattered in small pieces over extensive areas.