Iris Metals Ltd (ASX:IR1) has found high-grade lithium and caesium through drilling work at its Tin Mountain project in South Dakota, raising the expectation that its focal pegmatite could have multi-mineral potential.

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The company has been carrying out phase one diamond drilling at Tin Mountain, picking up intercepts such as 5.2 metres at 2.05% Li2O (lithium oxide) from 39.2 metres, including 1.5 metres at 3.04% Li2O from 40.8 metres in one hole.

Yet another hole had the following: One metre at 1.54% Cs2O from 31.2 metres.

Iris completed all holes in this phase of exploration – which comprised 23 holes for 1,122 metres – late in 2024 and is now moving to Phase Two, which will focus on deeper and central core pegmatite zones with horizontal drilling.

The company will also carry out mineralogical mapping studies alongside its next drilling phase to develop a maiden mineral resource estimate.

Phase one drilling showed the main pegmatite extends down-dip under cover, is open at depth, and has mineralisation near-surface (whose qualities are now confirmed).

President of U.S. Operations Matt Hartmann said this work indicated Tin Mountain had multi-mineral potential. “The Phase I drill results at Tin Mountain confirms high-grade mineralisation and the multi-element potential of the host pegmatite, including lithium and now caesium,” he said.

“Plans for Phase II are underway to target the central pegmatite zone which proved difficult to access with a conventional surface drilling approach.

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“Iris will leverage extensive surface exposure and historic mining operations, combined with 2025 advanced technologies, to deepen our understanding of the Tin Mountainproject and advance towards a maiden mineral resource.”

Iris shares have been trading at 23.5 cents.

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