Best Methods for Opal Mining
Opals are formed in both sedimentary and volcanic rocks. Nearly 100%of Australia’s opal production is derived from sedimentary opal deposits.
All the Australian opal fields are situated in arid inland areas with little relief; and the opal is found at shallow depths, usually less than 30m, in deeply weathered rock in which there has been considerable silica movement.
Read more at the Australian Opal Association
Noodling for Opals:
Many locals search through heaps of discarded mullock for pieces of precious opal. An abandoned open-cut mine is another good place for a noodler, using a rake and sieve for tools. Some have taken to large scale machine noodling by allowing large amounts of opal dirt travel on a conveyer belt under ultra-violet light, which detects the precious opal
Open Cut Opal Mining:
Open cut method is done by the use of heavy machinery to remove large amounts of opal dirt from closer to the surface for inspection. This method is more expensive and is mostly used to search for boulder opal in Central Queensland.
Puddling and Rumbling:
A Puddler is a large mesh-lined drum attached to a motor. This device rotates and turns the clay into sludge as water is pumped into the drum. The sludge escapes through the mesh. A related technique is dry rumbling
Sink a Large Shaft:
The simplest form of opal mining is by shaft sinking with a pick and shovel. A shaft is sunk straight down until some promising “opal dirt” is discovered. Length of the shaft could be as short as three metres or as long as 20 metres. A handpick or screwdriver is used to extract any opal found, due to the frailty of the stone.
