Opal mines are amazing and dangerous places. Most people imagine mines to be like a coal mine, a diamond mine, or a gold mine, but actually, an opal mine is relatively small.
Here in Lightning Ridge, an average opal mine is a 50-meter by 50-meter block of land. Compared to a coal mine that may be kilometres across. Small operators run Opal mines in groups of 1 to 4 people. Small machinery is used chiefly all run by hydraulics or air compression.
The first step to starting an opal mine in the ground is to find an area with good opal trace. The only way to find trace is to drill or dig down till you get the opal bearing level and see if the site is rich in opal trace. Bigger miners use a 9-inch drilling rig to test the levels for opal. Once the drilling rig has traced the opal, a larger drill is used to drill down a hole big enough to fit a person and some machinery down it (usually a 3-foot drilling rig). Back in the early days, they used to dig with a pick and shovel to get down, but now it is much faster.
A ladder is placed down the hole and a hoist bucket attached to the ladder to hoist the dirt up the hole into the truck.
There are different ways to mine once you are down there. The first way is to use electric jackhammers and shovels, but that is a lot of hard work. The next way is to have a hydraulic digger, much like a backhoe. It is disassembled to get down the hole and then reassembled to start digging. The arm on the digger has teeth on it to rip the dirt out of the wall.
The most advanced way of retrieving the opal bearing dirt up the hole is using a blower machine. A blower is a 9-inch pipe connected to a massive fan on top of the claim that sucks air and rock through the pipes, up the shaft and into a truck waiting at the top. Once the truck is full, the opal dirt is taken to a place called an agitator site, where a cement truck has been disassembled and reassembled into an opal washing machine called an Aggy. The dirt is then washed in the aggy by tumbling it round and round and adding water to loosen the mud and sandstone from potential opal pieces. If the barrel of the Aggy is turning too fast, the possible opal from the mining dirt could break on the walls of the agitator. So a slow pace is set.
The opal washing process can take from 2 hours to 3 days, depending on the mined opal dirt’s hardness.
Once all the opal dirt has washed away, you are left with the harder pieces like sandstone, ironstone and opal, if you’re lucky.
The agitator is then turned in reverse so the potential opal in the tail out can pour onto an opal sorting tray table to be picked up by the miner. This time can be one of the most exciting times for the miner, for it could have hundreds of thousands of dollars in the tail out, or there could be nothing. And usually, there is nothing. But the opal fever keeps the opal miner coming back for more, just like a poker machine to try their luck in Lightning Ridge. For more information on opal cutting or purchasing opal.