Aterian (LSE:ATN) announced it has secured a four-year extension to its exploration licence for the Kinunga project, also known as HCK, in southern Rwanda, granted by the Rwanda Mines, Petroleum and Gas Board.
The London-listed, Africa-focused critical metals explorer said the renewal underpins a staged evaluation of recovering tantalum and niobium from the weathered upper portions of Kinunga's pegmatites, alongside continued exploration of lithium mineralisation in the fresh rock beneath.
Rio Tinto completed its earn-in at HCK in October 2025 after spending $4.73m on exploration, handing control of the project and a full technical dataset back to Aterian, including diamond drilling results such as a 6.90-metre intercept grading 2.11% lithium oxide.
Aterian is now in discussions with potential technical and development partners, including a specialist mineral processing consultancy, to test recovery of fine and ultra-fine tantalum-bearing material that artisanal processing typically loses to tailings.
The testwork is intended to inform the design of a wash plant at Kinunga, potentially incorporating a complementary fines-recovery circuit to lift overall metal recovery.
Charles Bray, Aterian's chairman, said the company sees "significant potential to build value at Kinunga by combining the project's mineralisation and existing exploration database with specialist processing expertise and our established operating and trading presence in Rwanda."
Bray said a successful staged development could provide concentrate with documented mine origin and a route to market through the group's trading business, and that the immediate goal is to establish whether weathered material can support a commercially attractive tantalum-niobium operation.
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The next steps, he said, are to establish recovery performance and concentrate quality before determining an appropriate pilot programme and development economics.
Separately, Aterian will assess whether the same fine-material recovery approach could apply to selected tailings and stockpiles from artisanal and small-scale mining operations, potentially supporting a small modular recovery unit with concentrate marketed through its existing trading arm, Eastinco.
Any development decision remains contingent on satisfactory technical and economic studies, confirmation of sufficient mineable material, funding, definitive agreements and regulatory approvals, and no binding partnership has yet been concluded.
Aterian is also defining exploration priorities and expenditure for the enlarged Musasa project area in Rwanda's Western Province, with further details to follow as the work programme and budget are finalised.