Processing … separating the dirt from the opal
In1956 Arthur Molyneux made a new kind of dry puddler for separating the nobbies (opal nodules) from the softer claystone in which they occurred.
This design was improved on by using heavy steel mesh for the drum, and a rotating circular plate with three beaters at the bottom of the drum to break up the dirt.
Puddlers provided an effective way of processing the mounds of dirt left around hundreds of abandoned shafts on the old opal fields.
In the 1960s, with more water available from bores and dams, many miners added pumps and sprays to their puddlers to improve their efficiency and reduce opal breakage. In these wet puddlers, the water mixed with the fine clay dirt to make a slurry which escaped more easily than dry dirt through the mesh walls of the drum.
During the 1960s Eric Catterall, and other miners wanting to process larger quantities of dirt, began using rumblers, large cylinders with steel mesh walls which rotated slowly around a horizontal axis. The movement broke the clay dirt down to a fine dust, or to a slurry if water was added, leaving the harder claystone and opal behind to be removed and sorted later. Many variations were made in the designs of rumblers to improve their effectiveness.
In 1975 Gary Stone had built one of the largest wet rumblers but he found it needed too much repair when processing large volumes of dirt. He bought an old cement mixer and modified it for processing – this proved to be far more effective.
To reduce operating costs, some miners installed vibrating screens to separate the larger rocks from the smaller lumps of rock and claystone before feeding dirt from the mines into agitators.