Toronto, March 7, 2025 — The Prospectors & Developers Association of Canada (PDAC), a leading global mineral exploration and development community, has awarded the 2025 Thayer Lindsley Award to the Onto Deposit Discovery Team. This award is given to individuals or exploration teams who have made a significant discovery with economic feasibility potential. The Onto Deposit Discovery Team consists of experts from PT Sumbawa Timur Mining (STM), Vale Exploration Pty Ltd, and PT Vale Eksplorasi Indonesia.
Since the discovery of the Onto Deposit in 2013, in-depth studies and further exploration have been carried out by PT Sumbawa Timur Mining, known as the Hu’u Project. This world-class copper–gold deposit has an estimated resource of approximately 2.1 billion tonnes, with each tonne containing 0.86% copper (Cu) and 0.48 grams of gold (Au). The economic significance of the Onto Deposit, combined with its technical challenges and the innovative exploration methods used, led to the team being recognized for their contribution to the global mining industry.
On its official website, PDAC stated that the Onto Deposit is an extraordinary “blind mineral discovery.” The discovery was made in a densely forested mountainous area with no surface mineralization, through deep drilling (holes up to 800 meters) following mapping, river sediment and soil sampling, and airborne geophysical surveys (LiDAR, magnetic, and radiometric). The deposit is located 500 meters below the surface, hidden beneath a layer of unmineralized volcanic rock.
The award was presented on March 4, 2025, during the PDAC Awards Gala & Nite Cap event held in Toronto, Canada. This event honors outstanding achievements in the global mineral exploration and mining industry. In addition to the Thayer Lindsley Award, other award categories include the Bill Dennis Award, Skookum Jim Award, Sustainability Award, and Viola R. MacMillan Award. STM congratulates all the outstanding winners!
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About PT Sumbawa Timur Mining
PT Sumbawa Timur Mining (STM) is a joint venture company between PT Aneka Tambang Tbk (20%) and Eastern Star Resources Pty Ltd (80%). STM manages the Hu’u Project, a copper exploration project operating under a 7th Generation Contract of Work (CoW) located in Hu’u Subdistrict, Dompu Regency, West Nusa Tenggara Province, Indonesia.
The CoW area also contains geothermal resources. To explore this potential, STM established its affiliate company, PT Sumbawa Timur Geothermal, which has received a Geothermal License (IPB) from the government. STM continues its journey toward realizing its vision of becoming a world-class copper mining operation powered by renewable energy.
For more information, please contact the STM Communications Team.
