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  • Resource Estimate of The Onto Deposit Increases to Over 2 Billion Tonnes 

    21 / 04 / 2022 Press Release

    Sumbawa Timur Mining

    Content Significant Copper and Small Amount of Gold

    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 2.1 billion tonnes (Bt) with each ton containing 0.86% of copper and 0.48 gram of gold. Details of these updated mineral resources estimated as follows: 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 first public announcement of the Onto Deposit mineral resource estimate in December 2019 reported a total Inferred 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. This represents an increase in the size of the Onto deposit of 0.4 Bt or equivalent to >20% since the announcement of the first 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 estimate strengthener 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 in 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.


    About PT Sumbawa Timur Mining – PT STM

    PT Sumbawa Timur Mining (STM) is a joint venture between Eastern Star Resources Pty Ltd (80%), a subsidiary of Vale SA, and PT Antam Tbk (20%). Established in 1998, STM is the manager of the Hu’u Project through the 7th generation Contract of Work (KK) in Hu’u District, Dompu Regency, West Nusa Tenggara Province, Indonesia. The area of KK is 19,260 hectares, covering Dompu Regency and Bima Regency. Currently, PT STM is carrying out mineral exploration activities to create a world-class copper mine supported by geothermal renewable energy.

    For further information, please contact Sumbawa Timur Mining Team


    Sumbawa Timur Mining
    Sumbawa Timur Mining