Mining Techniques
Opal is a very elusive gemstone when it comes to prospecting and mining. The occurrence of precious opal remains a field of endeavour that requires much scientific work in order to develop suitable prospecting techniques to uncover where the gemstone is hidden. Opal is not like diamonds or other minerals such as coal, which can be prospected for over a large scale area with confidence. For the present, the sporadic nature of precious opal in the opal dirt or opal environment remains elusive to the large scale mining company. So opal mining remains the realm of the small miner or group of miners in partnership.
Hand Windlass and York Hoist White Cliffs opal field NSW.
Historical methods
Early days of opal mining prior to the opal mining “industrial revolution” were limited to digging opal mines by hand with pick and shovel. Prospecting was done by divining (although some miners still use “the wires” today). Lighting was provided by candlelight and the opal dirt was brought to the surface by hand windlass in “buckets” often not larger than a ‘four gallon drum’ (20 litre). Mine safety was almost non existent as was any idea of modern environmental conservation issues and mine rehabilitation.
A self-unloading hoist Coocoran Opal Fields Lightning Ridge precious stones field.
The small miners opal mining methods
Opal mining through historical times been considered the realm of the “small miner” with opal mining leases and tenements being limited in size. For example in Lightning Ridge , two (2) 50m x 50m square blocks. Whilst the shafts drilled for opal mining are still typically “Three foot holes” the extraction of opal dirt was by simpler methods than applied in larger mining operations.
Miners would extract the opal dirt by using “pick and shovel”, or perhaps a pneumatic hammers, and bring the “ore’ to the surface with a “self unloading hoist” (self unloader) before further processing.
Modern Mining
Today there are many innovative pieces of equipment used and designed specifically for extracting opal from the available precious stones fields. Government regulations for miners both in the proclaimed mining areas and in areas of occupational health and safety are impacting miners in all fields. There are differences between each of the states of Australia as well as mining districts within each state both in methods and legal requirements. In a broad discussion different fields require different equipment, for example opal mining at Lightning Ridge uses substantial amounts of water to wash the opal dirt, whereas in South Australia there is not sufficient water available and much processing is done dry. In Queensland boulder opal fields the opal is in levels of boulders and so large equipment such as bull dozers are predominate.
prospecting with a 9”auger
SINKING A “THREE FOOT” HOLE
WORKING UNDERGROUND
PROCESSING THE OPAL DIRT
LIGHTNING RIDGE
COOBER PEDY
OPAL PROSPECTING - AUSTRALIA
Each of the three states in Australia have different procedures for prospecting and mining for opal. In each state the first part of the process is to obtain either an opal prospecting license or an opal mining claim.
