Jakarta, – 21 April 2022 – PT Sumbawa Timur Mining (STM) announced today a newly concluded mineral resource estimate of the Onto copper-gold deposit in Nusa Tenggara Barat Province. The mineral resource estimate, which was completed in December 2021, reported a total Indicated mineral resource of 1.1 billion tonnes (Bt) @ 0.96% Cu and 0.58 g/t Au and a total Inferred mineral resource of approximately 1.0 Bt @ 0.7% Cu and 0.4 g/t Au.

The December 2019 mineral resource estimate reported a total Indicated mineral resource of 0.76 Bt @ 0.93% Cu and 0.56 g/t Au and a total Inferred mineral resource of 0.96 Bt @ 0.87% Cu and 0.44 g/t Au. The December 2021 mineral resource estimate increases the size of the Onto deposit by 0.4 Bt. This equates to a >20% increase since the December 2019 mineral resource estimate.

The Onto deposit is part of STM’s Hu’u Project, which is a 7th generation Contract of Work (CoW) entered into with the Government of Indonesia on 19 February 1998 located in Dompu and Bima Regencies in Nusa Tenggara Barat. STM is majority owned (80%) by Vale S.A., through Eastern Star Resources Pty Ltd, and Antam Tbk (20%).

Bede Evans, President Director of STM,said,“This latest mineral resource estimatestrengthensour view that the Onto deposit has the potential to be developed into a world-class copper mining operation. The increase in the Onto mineral resource by 0.4 Bt is the result of the effort, support and commitment of the Hu’u Project team over the last two years. This provides the STM shareholders and the STM team with cautious optimism as we enter into more advanced stages of project development .”

STM has conducted exploration activities within the Hu’u Project CoW since 2010. The mineral resource estimate is based on 74 holes, with a total length of 74,130 meters, drilled into the Onto deposit. Drilling will continue in 2022 and beyond to support studies to further define the size, extent and characteristics of the mineral resource and provide input to engineering studies. In total, STM has completed 108 drill holes (115,591 meters) within the CoW (at Onto and other prospects) since exploration began in 2010.

Mr Evans continued, “Whilst we are very pleased to report an increase of the Onto deposit mineral resource, much work remains to be undertaken to assess technical, environmental, social and financial factors as part of our ongoing feasibility studies. Ultimately, it is our hope that these feasibility studies will define a technically and economically viable mining operation for STM to take into further development.”

Hashari Kamaruddin, Director of STM, reaffirmed his confidence on the Hu’u Project, “I am very pleased with the progress of the Hu’u Project and the new mineral resource statement announced today. The strong collaborative relationship between the STM shareholders and the solid support from the Government of Indonesia and Government of West Nusa Tenggara Province gives us confidence that the Hu’u Project has the potential to be a significant mining operation in Indonesia.”

STM is currently undertaking feasibility studies aimed at further mineral resource definition and to assess hydrogeological, geothermal, and geotechnical characteristics of the deposit. Several technical challenges need to be overcome as part of the feasibility studies in order to confirm that the Onto deposit and Hu’u Project can be developed into a world-class underground mining operation.

Media Enquiries:

Agus Hermawan
Communications Specialist
PT Sumbawa Timur Mining
Email: Agus.Hermawan@vale.com Phone: +62 81113109544

Siaran Pers
Press Release – Resource Estimate of the Onto Deposit Increases to over 2 Billion Tonnes.pdf