Prospecting for opal has always been an uncertain activity. Most of the known deposits have been found because of the occurrence of small pieces of weathered opal on the ground surface, indicating the probable presence of the gem nearby. Because of the extreme dryness of the climate in the Australian opal fields and the lack of regular runoff of water, the opal weathering out has tended to stay on the surface near the matrix sediments from which it has weathered. This is in contrast with the Brazilian deposits, where higher rainfall and more regular streams have resulted in some opal being recovered from alluvial deposits.
In most cases, opal has been found by local residents of the areas; not by the professional prospector. Once the first deposits have been exploited, the prospector and miner then fan out from the initial discovery area, sinking shafts in the hope of cutting an opal horizon. This has been the history of all of the major opal fields of Australia.

Once the initial areas of discovery have been pegged out and tested, with some claims being profitable, others barren, prospectors may sink shafts in nearby areas. Many extensions of the original fields, have been discovered in this way, especially in the Lightning Ridge and Coober Pedy areas.

Systematic exploration is usually carried out by a drilling program using calyx drills of about 30 cm diameter. The shafts are put down to the opal level, which can usually be recognised by the occurrence of potch, hard bands, or other changes in lithology. Because of the speed with which the holes can be drilled, together with the technique of spreading the base of the holes at the opal level, it is not uncommon for small amounts of opal to be recovered in the neighbourhood of known fields, thus helping to finance the exploration.

The earliest opal deposits to be worked in Australia were close to the surface, but as these were mined out, it was realised that the 'opal levels' could be found at greater depths. Shafts were usually rectangular in shape and about one metre by 0.7 metre. These were laboriously dug by hand to depths of up to 30 metres and ladders, or merely ropes, were used to climb in and out of the mines. Two or three men usually mined each lease, with the surface man using a hand windlass to haul buckets of barren or opal-bearing ore to the surface. This mullock was dumped around the mouth of the shaft, which was timbered above ground level, resulting in the patterns of small, white 'craters' so strikingly seen from the air.

The shafts were sunk to about 1.5 metres below the opal level. These levels could be recognised by certain characteristics in each field. At Andamooka, for example, the opal was mainly confined to a band of silicified conglomerate some 30-40 cm thick.

Today, the washing machine has graduated to the use of the large mixers of the type used for transporting concrete. The cleaned gravel is then screened, sorted and examined by hand to pick out any nobbies or other opal fragments.

The clay which is washed away has been tested for use as a pottery material. It a smooth clay, suitable for throwing on a wheel, and, using the appropriate techniques with regard to its firing characteristics, has potential as a pottery raw material. Such clay is already being used on a small scale, and handmade ceramics have been made and marketed in White Cliffs and Lightning Ridge.

In some areas, especially in the boulder opal fields of south western Queensland, and at Mintabie, where the host rocks are much harder, bulldozers are used to remove the overburden. When the opal level is reached, thin layers are scraped away, with men following the machine looking for opal. This system often yields opal quickly, although significant amounts may be lost.