• Phase I drilling confirms significant high-grade lithium and caesium intersections
• Drilling results demonstrate the pegmatite extends down-dip under cover and remains open at depth
• Phase II drilling will target deeper and central core pegmatite zones with horizontal drilling technology

IRIS Metals Limited (ASX: IR1) has announced the results of its Phase I diamond drilling program at the Tin Mountain Project in South Dakota, USA. The findings confirm high-grade mineralization and the multi-element potential of the pegmatite, including lithium and caesium. The Phase I drill program, comprising 23 holes for a total of 1,122m, demonstrated that the pegmatite extends down-dip under cover and remains open at depth. Significant intercepts include 5.2m @ 2.05% Li2O from 39.2m, including 1.5m @ 3.04% Li2O, and 1.0m @ 1.54% Cs2O from 31.2m. The Phase I targets focused on confirming the near-surface lateral extent of the pegmatite and exploring its down-dip extension. However, steep terrain and hazards from historical underground workings limited drill collar placement, adding complexity to the program. The area beneath the historical cavern and underground workings was not adequately tested using conventional surface core drilling methods and now represents the priority exploration target for Phase II. IRIS plans to deploy a horizontal drill rig positioned on favorable topography to advance lateral core holes beneath the existing cavern and underground workings, targeting the core of the zoned pegmatite. Additionally, the company is planning detailed mineralogical mapping of the outcropping pegmatite to compare mineral distributions between surface exposures and drill core, which will aid in assessing the megacrystic pegmatite and modeling work as IRIS advances Tin Mountain to a maiden mineral resource estimate.

IRIS is preparing for the 2025 field season with drill programs planned across the Beecher, Tin Mountain, and Edison Projects. An expanded airborne geophysics program is underway, building on the smaller survey completed in 2024, to define and permit drill-ready targets for 2025. The company continues to evaluate and conduct due diligence on potential acquisitions in South Dakota-based tenure to further strengthen its portfolio.