Opal mining isn’t easy, and opal isn’t easy to find. It takes hard work and sometimes many years to ‘strike it rich,’ if that happens at all. As the industry has developed, so has opal mining machinery. Even within Australia, machinery has evolved specifically for the unique terrain the opal miners find themselves in.
Finding Opal
When prospecting leases became available, miners would subcontract a driller who would come and test drill the area to try to find opal bearing dirt. Once miners found a site, the rig would place a one-metre hole (shaft) down to 20-30 metres to enter the mine. These claims were usually 50x50 metres, and opal miners could have two claims in their name.
Digging Opal
From here, miners would dig a tunnel called a ‘drive,’ perpendicular to the shaft, allowing the search for the opal to occur over a wider area. Miners would use tools such as a jackhammer to remove the ‘opal dirt’ and brought to the surface to be sorted. A hoist or blower is used, and the opal dirt is loaded onto a truck on the surface.
Sorting Opal
Trucks are then unloaded into a dry agitator. The opal bearing earth is tumbled and washed for several hours. At the end of this process, the remaining ‘tailings’ are sorted in the hope of finding the elusive opal. In the early days, agitators were dry. Still, when mining became more sophisticated, the miners association operated dams, and these ponds would be fed by artesian water, which also increased opal production.
The Search For Opal
Opal miners face many difficulties mining, so searching for opals is a challenging lifestyle. The conditions are severe, and only the tough survive. Living in parched desert camps where most campsites do not even have electricity, let alone internet access. Many bush camps have Hessian showers, effectively a bag hung from a tree, with cool water.
There are numerous ways to mine for opals:
- Open Cut
- Trench Searching
- Opal Divining
- Drilling
Open Cut Mining
This form of opal mining is costly because all of the dirt is extracted, but it does mean that concealed pockets of opal are never missed. Open cut mines need a significant bond, plus digging costs, machinery, and backfill costs even if no opals are found.
Trench Searching
An excavator digs a trench 3-4 metres deep or down to bedrock. Miners then climb down into the trench and inspect the sides for any opal bearing potch. Trenches are approximately 15 metres long.
Opal Divining
This is basically the same as divining for water, where a miner has a rod and can feel the rod move in the presence of water. In this case, some people will search areas where a particular scrub grows as an indication of underground opals. Many people have tested scientific instruments to find opal or slips in the earth, but none have been successful. Today, many miners will work old mines to find opals left behind or do open cut mining where they join several claims together.
Drilling
Opal miners purchase a lease to drill on land for a period of time. This involves using a drilling rig with a six or eight-inch drill to test drill an area to see any opal traces. Once a miner finds a good spot, a metre wide hole is drilled down to the opal bearing dirt level. It is an expensive operation if nothing is found.
Environmentally Sensitive Mining
Mine shafts must now be backfilled following mining, with a bond ensuring this occurs. These open-cut mines can be expensive to backfill and revegetate again. A relatively new method in Queensland Boulder Opal fields involves backfilling shallow excavations as the claim is worked. Some miners have used simply a standard backhoe on a tractor to test drill small claims and have recovered some large parcels of rough opals. Opal miners in Lighting Ridge typically do not use this method due to the deep depths of mines.