Before the opal miners start digging they need to apply for leases and prospect with a drilling rig. This drilling rig will go down to the bedrock and take samples that will be analysed for any opals. If opal is found they will drill a hole down from one to an average of 30 meters. Then the opal miner will work with a jack hammer or an earth moving equipment. Strong blowers will lift the dirt to the top and place them in the truck. In the past, hoist systems would be operated to lift dirt to the surface. The trucks would take the dirt to an agitator set up on the pond and the dirt would be washed to expose all the opals. There are only a few open cut mines at Lightning Ridge as there are expensive bonds and running costs required to operate open cut opal mines.
Opal Mining at Lightning Ridge
Pictures from left to right: Lightning Ridge, drilling rig in action and opal miner’s camp.
Opal dirt dumped into truck- Trucks dumping at pond site
Note trucks on wall of pond- new Agitator - old dry agitator no water needed to operate this machinery.
Australian opal fields have a long and colourful history. Here you can find fascinating insights into our most well known fields. The area marked in light yellow below indicates where the ancient Artesian inland sea once lay within this area Australia’s most famous opal fields operate. All types of precious opal are found in this vast area. The area marked inred indicates where the state of Queensland’s opal fields are found, home to the boulder opal.
Australian opal fields are so unique in the world. Opals from Queensland are mined on ironstone backing and black opals have unique black potch and Coober Pedy has many crystals formed as seam opals or fossil. Each area is so unique that opal miners can easily distinguish between what area the opal came from, however experienced opals miners can even tell at what level or what area from an opal field that the opal came from.
The Mining of Opal
Opal is well-known as a valuable gemstone which is generated from non-crystalline silica gel. It is composed of 2 to 5% of water and tiny silica spheres which are arranged in a standard pattern. It usually measures 5.5 up to 6.5 and based on MOH’s solidity’s scale with diamonds gaining a scale score of9 to 10. It is a birthstone for October.
During 1849, Opal was was found at a cattle station known as Tarrawilla, in Angaston. Nearly, 95% of the Opal is discovered in Australia. However, a small number has been found in areas like the USA, Brazil and Mexico. New opal fields in Ethiopia look promising. There are three main Opal mining districts in Australia that generate diverse types of Opal.
Most of the Opal deposits are found in New South Wales and South Australia and Queensland. Each field produces opals with certain features and color patterns. Lightning Ridge is considered as the most famous and magnificent black opal.
Coober Pedy is well-known for its Milky Opals. At present its opal fields include an area of roughly 45 kilometers. The Andamooka field is in the southwestern part of Coober Pedy in mostly desert country. Andamooka is one of Australia’s most prominent Opal fields, having generated some of the most striking pieces of Opal including the one known as the ‘Queens Gem’.
Most of these opal fields within the Andamooka area generate crystal, dark, gem, and light Opal. Opal regularly occurs in both sedimentary rocks and volcanic form. In fact, there is a variety of methods in mining an Opal. Generally, there is a far-reaching documentation that shows a collection for an Australian Opal.
Methods of opal mining
Drop a shaft:
This is the simplest way of mining opal through the use of shovel and pick. A shaft is submerged directly until some “Opal dirt” is exposed. The span of the shaft could be as too small as three meters or as extensive as 20 meters. A screw driver or handpick is used to take out with any Opal found because of the weakness of the stone. However due to the government regulations it is getting harder and more expensive for this type mining operation.
Open cut mining:
This procedure is done by the use of large equipment, bulldozers, excavators, to eliminate huge amount of dirt around the opal nearer to the face for inspection. This technique is more exclusive and is typically used to explore boulder opal in central Queensland.
Some have taken to huge scale machine noodling by permitting huge quantities of dirt around the Opal on a conveyer belt beneath ultra-violet light, which determines the valuable opal.
Puddling and Rumbling:
A puddler is a hefty mesh-lined drum fixed into a motor. These machines spin and twist the clay into the mire as water is forced into the drum. This mire runs through the mesh. An associated technique is known as dry rumbling.
Australian Opal Mining Industry
Currently, Australia produces approximately 95 per cent of the world’s opal from sedimentary rocks in central Australia. Other countries which produce minor amounts of opal include Honduras, Mexico, former Czechoslovakia and Brazil. With the exception of Brazilian opal, which is sediment-hosted, opal in these countries occurs in volcanic rocks. Sedimentary opal is superior in quality to volcanic opal.
All of Australia’s significant opal deposits are situated within or adjacent to the margins of the Great Australian Basin. The characteristics of opal deposits vary from field to field. The highest value stones are black opals from Lightning Ridge. Gem quality opals vary enormously in price. Unprocessed top quality black opal is currently worth up to $10,000 per carat. Lesser quality opal varies considerably in price depending on the type of opal, its colour, impurities and defects. The value of the industry to the Australian economy is unknown owing to its fragmented nature and inadequate official records. Production figures of between $100 Million and $200 Million per annum for uncut gems are generally quoted. Estimates from the various State governments support the more conservative figure.
Historically, opal mining has been the preserve of the small-scale miner, although each of the opal States (South Australia, New South Wales and Queensland) has either enacted legislation or begun promotion to encourage the larger-scale explorer and miner. Despite the vast expanse of potential opal-bearing rocks in central Australia, only one new opal centre (Lambina in South Australia) and few new significant discoveries away from existing centres have been made in the last 70 years.
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