Cosa Identifies Priority Drill Targets at the Darby Uranium Project, Athabasca Basin, Saskatchewan

Vancouver, British Columbia–(Newsfile Corp. – October 14, 2025) – Cosa Resources Corp. (TSXV: COSA) (OTCQB: COSAF) (FSE: SSKU) (“Cosa” or the “Company“) is pleased to report it has identified multiple high priority follow up drill targets at the Darby Project (“Darby” or the “Project“). Darby is a joint venture (the “Joint Venture“) between Cosa and Denison Mines Corp. (“Denison“) (TSX: DML) (NYSE American: DNN) and is located 10 kilometres west of Cameco’s Cigar Lake Mine in the eastern Athabasca Basin, Saskatchewan. Cosa is the project operator and holds a 70% interest with Denison holding a 30% interest.

Highlights

• Identification of highly prospective drill ready targets through extensive historical drill core and data review at the Delta and Charlie trends

• Multiple historical drill holes intersected features suggesting proximity to uranium mineralization – warranting direct follow-up

• Evaluation of remaining trends is ongoing and expected to produce additional priority targets at Darby

Keith Bodnarchuk, President and CEO of Cosa, commented: “Featuring prospective geology under modest sandstone cover and multiple historical intersections of uranium mineralization, the Darby Project was always a vital component of the transaction with Denison. These results further support Cosa’s thesis that Darby is a mature, discovery-ready project. We are eager to begin the approaching 2026 drilling season with highly prospective follow up targets at both Darby and Murphy Lake North. We are looking forward to finalizing drilling plans and budgets with our joint venture partner and largest shareholder, Denison Mines, and are thankful for their continued guidance and support.”

Andy Carmichael, VP Exploration of Cosa, commented: “Having applied the same target identification approach that led us to discover the Hurricane Deposit in 2018, we are very encouraged by the historical data and drill core. Darby has proven special in that it continues to improve the closer we look, and we are continuing to develop high quality targets in advance of winter drilling. Coincident alteration, illite, and chlorite plus broad zones of anomalous uranium in the lower sandstone are strong indicators of a uranium bearing system in the eastern Athabasca including at the nearby Cigar Lake mine.”

Darby

Located 10 kilometres west of the Cigar Lake Mine, Darby contains multiple prospective conductive trends and several historical intersections of weak uranium mineralization (Figure 2). Historical drilling has proven that many of these trends are highly prospective for uranium deposits of the eastern Athabasca Basin, yet the majority of the strike length has not been effectively tested. Work by Cosa in 2025 has prioritized these trends and identified several historical drill holes with results that suggest proximity to uranium mineralization.

Target Identification

A team of Cosa personnel led by Cosa’s Chairman Steve Blower and VP Exploration Andy Carmichael relogged all historical Darby drill holes in June. This work confirmed desktop interpretations and generated immediate follow up targets. Cosa interprets that of 31 drill holes on the Property targeting conductive anomalies only 13 (42%) explained their target and only six (19%) were effective evaluations of the targeted area, leaving over 80% of the Projects’ 40 kilometres of conductive strike length untested. Ongoing trend-by-trend assessment of drilling results has identified several trends as having distinctly greater exploration potential, including the Delta and Charlie trends (Figure 2). Evaluating alteration, structure, geochemistry, and clay mineralogy of individual drill holes has identified several with signatures potentially indicating proximity to uranium mineralization.

Delta Trend

The Delta trend in northeastern Darby contains more than 5 kilometres of conductive strike length targeted by limited historical drilling (Figure 2). Of the four historical drill holes at Delta only one intersected conductive basement rocks and none intersected the optimal target. The trend is considered highly prospective based on intersections of weak uranium mineralization in two historical drill holes and a broad zone of anomalous¹ sandstone uranium content proximal to graphitic basement faulting.

DB-27 Follow Up

Follow up of historical drill hole DB-27 is planned in 2026. The basal sandstone in DB-27 is pervasively bleached with illite and chlorite enrichment and includes a 52-metre interval of anomalous uranium content (Figure 3). In the basement, DB-27 intersected 0.13% U₃O₈ over 0.3 metres roughly 16 metres below the unconformity, and graphitic faulting 80 metres below the unconformity. The intersection of basement faulting with the unconformity is a high priority follow up target on section and along strike, further upgraded by the presence of anomalous uranium in the overlying sandstone.

Charlie Trend

The Charlie trend is also located in northeast Darby, is approximately 5 kilometres in strike length, and in part defined by modern EM surveying (Figure 2). Of the six historical drill holes at Charlie, three intersected conductive basement and only one is considered an effective test of the optimal target. The trend is considered highly prospective based on intersections of alteration and structure in both the sandstone and basement, and anomalous sandstone geochemistry. One drill hole has intersected weak uranium mineralization on trend (Figure 2).

DB-09 Follow Up

DB-09, the westernmost drill hole on trend, intersected multiple zones of elevated to anomalous uranium content in the lower 115 metres of sandstone (Figure 4). Notably, the basal sandstone contains continuously anomalous uranium over 42 metres, illite and chlorite enrichment, bleaching, and hydrothermal hematite. In the basement, DB-09 intersected graphitic faulting 30 to 60 metres below the unconformity. The intersection of these graphitic faults with the unconformity, proximal to highly anomalous uranium in the lower sandstone, is considered a high priority follow up target on section and along strike.

Ongoing Work

The Charlie and Delta trends are two of seven total conductive trends at Darby; thorough evaluation of the project is ongoing ahead of a winter 2026 drill program. Both Darby and Murphy Lake North (“MLN“) remain high priority projects for Cosa for the winter 2026 drill program. The Company is still awaiting outstanding analytical results for the MLN summer drill program which will be used to plan follow up drilling. Cosa and its joint venture partner, Denison Mines, are in the process of finalizing winter drill programs and budgets for Darby and MLN.

1 – When analyzed using SRC’s partial digestion and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) method, Cosa considers uranium concentrations in the Athabasca sandstone greater than 0.5 ppm to be elevated, greater than 1.0 ppm to be anomalous, and greater than 4 ppm to be strongly anomalous.

Figure 1 – Cosa’s Eastern Athabasca Uranium Projects with Joint Venture Projects

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Figure 2 – Darby Project Overview

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Figure 3 – Cross Section Through Delta Trend Drill Holes DB-27 and CLC4-9

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Figure 4 – Cross Section Through Charlie Trend Drill Hole DB-09

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About Cosa Resources Corp.

Cosa Resources is a Canadian uranium exploration company operating in northern Saskatchewan. The portfolio comprises roughly 237,000 ha across multiple underexplored 100% owned and Cosa-operated joint venture projects in the Athabasca Basin region, the majority of which reside within or adjacent to established uranium corridors.

In January of 2025, the Company entered a transformative strategic collaboration with Denison Mines 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 track record of success in Saskatchewan. In 2022, members of the Cosa team were awarded the AME Colin Spence Award for the discovery of the Hurricane uranium deposit. 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 focus throughout 2026 is drilling at the Darby and Murphy Lake North projects in the eastern Athabasca Basin. Both projects are operated by Cosa and are 70/30 joint ventures between Cosa and Denison respectively. Drilling at Darby is planned to test priority targets identified by thorough review of historical data and drill core and will target areas with anomalous uranium, clay alteration, and historical mineralization intersected nearby. Drilling at Murphy Lake North will follow up 2025 drilling which intersected broad zones of structurally controlled alteration over roughly 2 kilometres of strike length.

Technical Disclosure

Historical drilling and geophysical results for Darby were sourced from the Saskatchewan Mineral Assessment Database (SMAD). SMAD sources for Darby include file numbers 74H14-0021, 74H14-0023, 74H15-0041, 74H15-0053, 74H15-0055, 74H15-0056, 74H15-0066, 74H15-0067, 74I02-0031, 74I02-0042, 74I02-0053, 74I02-0080, 74I02-0095, and MAW00516. Some confidential data and reports not presently available via SMAD were supplied to Cosa by Denison.

Verification of drilling results included relogging of historical drill holes in the field to verify historical logs and interpretations, verifying historical drill hole collar locations from air photos, and verifying the collar location of DB-17 with a handheld GPS. Additionally, verification of geochemical results drill holes completed between 2008 and 2010 was facilitated by the reissuance of analytical certificates to Cosa by the Saskatchewan Research Council (SRC). Cosa thanks the SRC for its valued assistance in increasing confidence in the historical dataset.

Verification of historical geophysical results included determining the locations of geophysical survey grids from air photos, verifying grid line locations in the vicinity of drill hole DB-17, compiling all know historical geophysical 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, P.Geo., 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.

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Cautionary Statements

This press release contains forward-looking information within the meaning of Canadian securities laws (collectively “forward-looking statements”). Forward-looking statements are typically identified by words such as: believe, expect, anticipate, intend, estimate, plans, postulate and similar expressions, or are those, which, by their nature, refer to future events. All statements that are not statements of historical fact are forward-looking statements. These forward-looking statements or information may relate to anticipated exploration, development and/or expansion activities, including exploration of the Company’s current Projects; the collaboration with Denison, including the Joint Venture, and the anticipated benefits thereof; and the outlook regarding Cosa’s business plans and objectives.

Such forward-looking information and statements are based on numerous assumptions, including among others, that the results of planned exploration activities are as anticipated, the cost of planned exploration activities are as anticipated, that general business and economic conditions will not change in a material adverse manner, that financing will be available if and when needed and on reasonable terms, that third party contractors, equipment and supplies and governmental and other approvals required to conduct Cosa’s planned exploration activities will be available on reasonable terms and in a timely manner. Although the assumptions made by Cosa in providing forward-looking information or making forward-looking statements are considered reasonable by management at the time, there can be no assurance that such assumptions will prove to be accurate.

By their nature, forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or other future events, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors and risks include, among others: Cosa may require additional financing from time to time in order to continue its operations which may not be available when needed or on acceptable terms and conditions acceptable; Cosa may not be able to maintain compliance with its contractual obligations with third parties; Cosa may not be able to maintain compliance with extensive government regulation applicable to its operations; domestic and foreign laws and regulations could adversely affect Cosa’s business and results of operations; the stock markets have experienced volatility that often has been unrelated to the performance of companies and these fluctuations may adversely affect the price of Cosa’s securities, regardless of its operating performance; the ongoing military conflict in Ukraine, and other risk factors set out in Cosa’s public disclosure documents.

The forward-looking information contained in this news release represents the expectations of Cosa as of the date of this news release and, accordingly, is subject to change after such date. Readers should not place undue importance on forward-looking information and should not rely upon this information as of any other date. Cosa does not undertake any obligation to update these forward-looking statements in the event that management’s beliefs, estimates or opinions, or other factors, should change.

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