Mr. Keith Bodnarchuk reports

COSA IDENTIFIES TWO KILOMETRES OF STRONG SANDSTONE ALTERATION AND GRAPHITIC FAULTING AT THE CYCLONE TREND ON THE MURPHY LAKE NORTH URANIUM PROJECT

Cosa Resources Corp.'s summer drilling has identified two kilometres of highly prospective strike length characterized by strong sandstone alteration and graphitic faulting at the Cyclone trend on the Murphy Lake North project. MLN is a joint venture between Cosa and Denison Mines Corp., and is located in the eastern Athabasca basin, Saskatchewan. Cosa is the project operator and holds a 70-per-cent interest with Denison holding a 30-per-cent interest.

Highlights:

• Two kilometres of strong sandstone structure and alteration identified at the Cyclone trend underlain by large-scale graphitic faulting;
• Up to 30 metres of unconformity relief identified at Cyclone;
• Alteration and structure at Cyclone remain open in both directions, and follow-up drill targets exist along multiple trends;
• Cosa has met its solely finance obligation and owns an irrevocable 70-per-cent interest in Murphy Lake North.

Keith Bodnarchuk, president and chief executive officer of Cosa, commented: "The results of the Murphy Lake North summer drill program, specifically those at the Cyclone trend, are the most significant to date for Cosa, and further support our thesis that ample search space remains for the next uranium discovery in the infrastructure-rich eastern Athabasca basin. I want to thank Andy Carmichael and our field team for executing a successful program in a safe and timely manner. We would also like to thank our largest shareholder and joint venture partner Denison Mines for their continued support and enthusiasm for exploration at Murphy Lake North."

Andy Carmichael, vice-president, exploration, of Cosa, commented: "Summer drilling at Cyclone identified over two kilometres of highly prospective strike length and potentially identified an additional unexplored parallel trend to the south. The intensity and continuity of sandstone alteration and structure, both vertically and along strike, is an encouraging indicator of the trend's prospectivity. Basement structures intersected two kilometres apart are textbook examples of major graphitic faults critical to the formation of eastern Athabasca uranium deposits. With an average depth to the unconformity of roughly 250 metres, the Cyclone trend is incredibly well situated for the discovery of relatively shallow mineralization. Cosa and Denison have again elected to leave much of the drill equipment on site to minimize the time and cost to resume work in 2026."

Chad Sorba, vice-president, technical services and project evaluation, of Denison and technical adviser to Cosa, commented: "We congratulate Cosa for completing a safe and successful drill program on behalf of the Murphy Lake North joint venture. The structure and alteration observed at the Cyclone trend are encouraging and could represent early indicators of an eastern Athabasca uranium-bearing trend. These initial results illustrate the potential benefits of Denison's strategy to advance a portion of our large exploration project portfolio through joint ventures with capable and motivated partners. We are excited to continue working with Cosa to plan and execute a follow-up drill program at Murphy Lake North in early 2026."

Drilling program

Summer drilling at Murphy Lake North totalled 3,323 metres in eight holes completed as initial reconnaissance of the Cyclone trend and to follow up winter 2025 drilling results on the Hurricane trend. Positive results and greater exploration space led to a focus on Cyclone during the program.

Cyclone trend summary

Cyclone was drilled on four sections over 2.4 kilometres of strike length. Six of seven drill holes intersected positive results. The seventh is interpreted as an overshot of the optimal target. Drilling identified geology considered highly prospective for an eastern-Athabasca-style uranium deposit, including significant unconformity relief associated with major structures hosted within graphitic basement rocks. Faulting controls broad zones of alteration in the sandstone and basement, which are comparable with those associated with the region's uranium deposits. Weakly elevated radioactivity was intersected at the unconformity and in the basement, and is typically associated with hematite and/or clay alteration.

Results at Cyclone are exemplified by Section 2600E, where the broadest and strongest alteration and structure were intersected. Three drill holes on 2600E define a significant graphitic basement fault zone within a broader package of graphitic rocks associated with 30 metres of unconformity relief. Basement-rooted faulting is interpreted to extend through the entire 220-metre thickness of the sandstone as faulting is evident beginning at the top of bedrock. These vertically extensive structures control broad zones of hydrothermal alteration. In MLN25-010, nearly half of the sandstone is structured, including a 70-metre interval with strong fracturing, faulting, fault gouges, increased clay content and sections of near-massive clay, rotated sandstone bedding, strong bleaching, desilicification and decimeter-scale zones of increased radioactivity.

The continuity and intensity of alteration and structure are considered highly encouraging. The Cyclone alteration zone remains open in multiple directions and includes untested sections of up-to-1.2-kilometre strike length. With continued support from its joint venture partner and largest shareholder Denison Mines, Cosa will use pending geochemical results to guide follow-up drilling in early 2026.

Hurricane trend summary

MLN25-006 was completed as a 400-metre stepout from winter drill hole MLN25-004. MLN25-004 intersected a broad zone of alteration and structure in the lower sandstone (see Cosa's news release dated March 20, 2025). In MLN25-006, the lower 93 metres of sandstone displays strong bleaching, local clay alteration, and structure underlain by fault-controlled clay and chlorite alteration in the upper basement. MLN25-006 intersected improved alteration compared with MLN25-004, and additional follow-up to the east may be warranted pending geochemical results.

About Murphy Lake North

Murphy Lake North covers a portion of the Larocque Lake trend and is located 2.7 kilometres east of the Hurricane deposit. Hurricane is the world's highest-grade indicated uranium resource, and was discovered and delineated for IsoEnergy Ltd. by current members of Cosa's management, board of directors and advisers from 2018 through 2022. The Larocque Lake trend also hosts the high-grade Larocque Lake zone, Yelka prospect and Alligator Lake zone.

Per the completed acquisition agreement between Cosa and Denison (see Cosa's news release dated Jan. 14, 2025), Cosa has met its obligation to solely finance $1.5-million of exploration expenditures at the project during the summer drill program and now owns an irrevocable 70-per-cent interest in Murphy Lake North.

About Cosa Resources Corp.

Cosa Resources is a Canadian uranium exploration company operating in Northern Saskatchewan. The portfolio comprises roughly 237,000 hectares across multiple underexplored 100-per-cent-owned and Cosa-operated joint venture projects in the Athabasca basin region, the majority of which resides within or adjacent to established uranium corridors.

In January of 2025, the company entered a transformative strategic collaboration with Denison that has secured Cosa access into several additional highly prospective eastern Athabasca uranium exploration projects. As Cosa's largest shareholder, Denison gains exposure to Cosa's potential for exploration success and its pipeline of uranium projects.

Cosa's award-winning management team has a long record of success in Saskatchewan. In 2022, members of the Cosa team were awarded the AME Colin Spence award for their previous involvement in discovering IsoEnergy's Hurricane deposit. Prior to Hurricane, Cosa personnel led teams or had integral roles in the discovery of Denison's Gryphon deposit and 92 Energy's GMZ zone, and held key roles in the founding of both NexGen and IsoEnergy.

The company's core focus throughout 2025 is drilling at the Murphy Lake North joint venture. Murphy Lake North is a 70/30 joint venture between Cosa and Denison, respectively, and is located at the northern end of the Larocque Lake trend. The project is within three kilometres of and on trend with the Hurricane deposit. Drilling completed by Cosa in 2025 identified multiple zones of strong sandstone structure and alteration, and weakly elevated radioactivity underlain by large graphitic structures rooted in basement rocks. The company is planning additional follow-up work in 2026.

Technical disclosure

Drilling completed by Cosa and reported in this news release was completed with oriented NQ diameter drill core, which was logged and sampled to capture geological information, including alteration, structure and radioactivity. All drill core was systematically scanned for total gamma radioactivity using an RS-125 hand-held spectrometer and the average counts per second recorded for each three-metre drill run. Intervals measuring over 1.5 times background levels were broken out and recorded. For intervals with elevated (greater than 300 cps) radioactivity (RS-125), total gamma radioactivity was measured by removing sequential 0.1-metre lengths of drill core to an area with background radioactivity and scanned with an RS-125.

Following completion of each drill hole, downhole total gamma logging was completed using a Reflex EZ-Gamma system lowered inside the drill rods using the drill wire line. Measurements of total gamma were collected every 0.1 metre in both the down and up directions. Downhole gamma logs were plotted alongside RS-125 total gamma measurements to confirm depths and hand-held spectrometer readings, and assess total gamma radioactivity through intervals of unrecovered core.

Composite sampling was completed throughout every drill hole. Composite samples are used as representative samples over varying interval lengths depending on geology, and are collected by taking half-core chips, approximately one inch long, every 1.5 metres. Spot samples are collected through zones of elevated radioactivity, alteration zones and other geological features of interest, and are taken as half-core samples between 0.1 and 0.5 metre in length. Samples were transported by company personnel or by courier to SRC Geoanalytical Laboratories in Saskatoon, Sask. (ISO/IEC 17025:2005 accredited), for multielement analysis. Certified reference material standards and CRM blanks were inserted into both the spot and composite sample series. SRC independently conducts a quality assurance/quality control program comprising repeat analyses and insertion of CRM standards. CRM results are verified by Cosa staff.

Historical drilling and geophysical results for Murphy Lake North and adjacent projects were sourced from the Saskatchewan mineral assessment database. SMAD sources for the Murphy Lake North project include file No. 74I-0060, 74I09-0057, 74I09-0064, 74I09-0066, 74I09-0077, 74I09-0098 and MAW00510. Data and reports related to the 2020 ground electromagnetic survey completed by Denison are not currently available through SMAD and were supplied to Cosa by Denison.

SMAD sources for drilling and geophysical results proximal to Murphy Lake North include 64L05-0161, 64L05-0180, 74I-0066, 74I-0067, 74I01-0114, 74I08-0056, 74I09-0053, 74I09-0061, 74I09-0064, 74I09-0071, 74I09-0079, 74I09-0087, 74I09-0088, 74I09-0090, 74I09-0091, 74I09-0092, MAW01939, MAW02327, MAW02599 and MAW02395.

Historical drill hole collar locations for Murphy Lake North and relevant along-strike drill holes were verified from air photos. The collar locations of Murphy Lake North drill holes CRK-144 and CRK-145 were verified on the ground using a hand-held GPS and determined to be within 20 metres of the locations derived from air photos. Segments of drill core from CRK-143 and CRK-144 were reviewed in the field. Further review was hampered by the deteriorated condition of core boxes.

Verification of historical geophysical results included confirming the locations of geophysical survey grids from air photos, compiling data from geophysical surveys completed postyear 2000, engaging a consultant to reinterpret historical geophysical surveys completed inside MLN and comparing with historical interpretations, and evaluating whether interpreted geophysical results could be reasonably explained by historical drilling results.

Qualified person

The company's disclosure of technical or scientific information in this press release has been reviewed and approved by Andy Carmichael, PGeo, vice-president, exploration, for Cosa. Mr. Carmichael is a qualified person as defined under the terms of National Instrument 43-101. This news release refers to neighbouring properties in which the company has no interest. Mineralization on those neighbouring properties does not necessarily indicate mineralization on the company's properties.

We seek Safe Harbor.