The first digital opal map for the Australian continent, showing where gem-quality opal is most likely to be found, has been created by a team of researchers at the University of Sydney.
The research was recently published in the Journal of Australian Earth Sciences and in Computers & Geosciences.
Opal is Australia’s national gemstone but no new significant opal discoveries have been made since the early 1900s. Most opal exploration is carried out by individual miners digging in desolate areas around old opal fields in the Great Artesian Basin.
“Unlike in gold exploration, there are no accepted concepts or methodologies available to guide opal miners where new fields may be found, and there are as many theories as there are opal miners,” said Dr Adriana Dutkiewicz, part of the opal research team from the University’s School of Geosciences.
Using cutting edge data mining strategies the team has developed a methodology that will help opal miners concentrate their efforts on areas that have not been explored previously.
The researchers were able to pinpoint a number of new ‘hotspots’ that are favourable for finding gem-quality opal by combining a multitude of digital geological and geophysical data sets.
“The geological conditions under which opal formed resulted from a very particular sequence of surface environments over geological time,” said Dr Thomas Landgrebe, the team’s data mining expert.
These conditions involved alternating shallow seas and river systems followed by uplift and erosion. The environmental changes occurred from about 145 million years ago (during the Age of the Dinosaurs) until the present-day and shaped the surface of vast parts of outback Australia.
Most Australian opal is found in the Great Artesian Basin but the new digital opal prospectivity map dramatically reduces the area where a good opal find is likely from 1.35 million km2 to 0.08 million km2.
The most likely locations for new opal fields occur along the south-western extent of the Great Artesian Basin in South Australia, in a northwest–southeast corridor throughout central Queensland and in areas around Lightning Ridge in NSW.
Interestingly, a new opal field was discovered last year 75km southwest of Lightning Ridge.
“This is precisely an area where our new map, which was completed before that discovery was made, suggests high opal prospectivity” added Professor Dietmar Müller, who holds an Australian Research Council fellowship to study the evolution of the Australian continent.
This gives credence to the team’s approach to mining data through geological time and space and suggests that other areas highlighted on the map may be promising new opal fields.
“The Great Artesian Basin’s future looks bright and colourful. Perhaps it’s time for me to buy an opal drill rig, take my long service leave and go underground for a while,” joked Professor Müller.
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