Discovery Of Additional High-Grade Mineralization At Gryphonv

TORONTO – Denison Mines Corp. announced the discovery of additional high-grade mineralization approximately 40 metres outside of the previously estimated mineralized domain associated with the D1 lens of the Gryphon uranium deposit. Drill hole WR-837AD2 intersected 2.3 metres at 1.69% eU3O8 including 0.5 metres at 5.48% eU3O8 in the down plunge direction from the previously defined D1 lens. This area remains open down-plunge and along strike to the northeast for further expansion. Gryphon is situated approximately 3 km northwest of the Company’s flagship Phoenix In-Situ Recovery (ISR) uranium mine development project.

The discovery was made as part of a highly successful delineation drill program carried out at Gryphon during the first half of 2025. Results from the delineation drilling are expected to add confidence to the previously estimated mineral resources for Gryphon, having confirmed the current geological interpretation of the deposit and intersecting uranium grades in line with expected values.

President and CEO, David Cates, said, “Our 2025 Gryphon delineation program was highly successful and achieved each of the program’s key objectives – including (a) increasing the density of drill testing within the A1 high-grade domain and confirming the geological model, (b) collecting additional geotechnical, metallurgical and hydrogeological samples and information to support future project evaluation efforts, and (c) initial testing of areas identified for possible expansion of mineral resources that are outside of the mine design outlined in the 2023 Pre-Feasibility Study (PFS).

The delineation results demonstrate that Gryphon is an excellent high-grade basement-hosted uranium deposit that justifies further project development evaluation and de-risking. With a focus on confirming the mineralization in the A-series of lenses, a limited number of drill holes were designed to test for possible expansion of the estimated mineral resource. As a result, we are excited that drill hole WR-837AD2 encountered high-grade mineralization outside of the existing mineralized domain in an area that remains wide open for further expansion down-plunge and along strike. We are currently developing plans to follow-up this result and test other expansion targets.”