SEG Discovery, No,142, July 2025, p19-35, Society of Economic Geologists
THE SEG invited industry experts to prepare a series of 31 technical papers to inform early-career geoscientists and geoscience students about the practical aspects of economic geology and related sciences of metallurgy, geotechnical engineering and mining engineering. These papers were published in various editions of the SEG’s Discovery Journal over the last 3 years. They were subsequently compiled into a special publication titled “Geology and Mining: Evolution of Best Practice” which was launched at SEG’s Conference in Brisbane in September 2025.
My contribution to this endeavour was to write a high-level overview of the major trends in mineral exploration over the last century.
The key observations from my Paper were:
■ An estimated 15,000 significant mineral deposits have been found in the world to date, with half of these discoveries made since 1960. Discovery rate is presently 70 to 90 deposits per annum, down from a peak of 202 discoveries in 2009.
■ In the early 1900s over half of all discoveries were made in just three countries—Australia, Canada, and
the United States. Today, their share has dropped to around 30%. In their place, Africa, Latin America, and
China have risen in importance.
■ While gold and base metals (mainly copper) continue to be the main target of interest, there have been
extended periods where uranium, bulk minerals, and more recently, lithium have taken center stage.
■ Since the 1950s, discoveries are being made under progressively deeper cover. From 2010 to 2019, the average depth of cover for gold discoveries was 56 metres, and the depth for base metal discoveries was 193 metres.
■ In the early 1900s, three-quarters of all discoveries were made by prospectors. Since then, their share has shrunk to less than 10%. In its place, the role of geologic mapping, geophysics, and geochemistry has risen in importance. The relative share for these exploration tools varies by target scale, commodity type, region, and depth of cover.
■ In spite of the challenges of exploring under progressively deeper cover, the industry continues to use
new tools and methods for discovery. Over 80 key innovations have been identified in the last 80 years.
Looking forward, the same rate of innovation is likely to continue.
■ With regard to copper, it appears that the world is discovering enough new metal to meet its future growth needs, unless demand increases markedly. However, a large part of this increase is growing the resource base of past discoveries rather than making new deposit discoveries. Not all discoveries get developed, and those that do can take several decades to advance to production.
■ The average size and grade of open pit copper deposits has been slowly declining over time. In the future, more deposits (both base metal and gold) will be mined underground.
■ Over the last four decades, there has been a major change in who is making discoveries in the Western world. In the past, it was mainly major companies and governments. Both have now been replaced by junior explorers, with their share increasing from 10% in 1980 to 77% in 2023.
■ Over the last two decades there has also been an extremely large increase in the amount spent on mineral exploration—up from $4.0 billion in 2002 to a boom peak of $43.8 billion in 2012. Expenditures are currently about $17 billion per year (in constant December 2024 U.S. dollars).
■ Of major concern is that the rapid increase in expenditure did not translate into a similar rise in the number of discoveries, in part since this funding inflow caused labor and drilling costs to rapidly rise in real terms, creating a major issue. Furthermore, the average target quality declined as players were crowded out of the best districts.
■ While some of the above issues have reversed in recent years, the average unit cost per discovery still remains significantly higher than what it was before the boom, and is currently about $200 million per significant deposit discovered.
The learnings of the recent exploration boom-and-bust cycle highlight the need for investors, exploration managers, and geologists to focus on funding and locating only perceived high-quality targets to test, increasingly under cover, as these have the best chance of delivering a high-value discovery.