Cosa starts drilling at Darby with Denison

Executive Summary

• Cosa Resources Corp. has commenced its Winter 2026 drilling campaign on its Darby project, with drilling at the Murphy Lake North (MLN) project to follow.
• Both projects are joint ventures with Denison Mines Corp., with Cosa holding a 70% interest and acting as operator.
• The campaign aims to test priority targets identified through 2025 core relogging and reinterpretation, focusing on zones of coincident sandstone alteration and anomalous uranium content near graphitic basement faults.

Key Details

• Darby Project Drilling Plan:
  • Approximately 2,500 metres of drilling are planned for Winter 2026.
  • Focus is on testing initial priority targets identified by Cosa's 2025 core relogging and reinterpretation program.
  • Targets include immediate vicinities of drill holes intersecting zones of coincident sandstone alteration and anomalous uranium content proximal to significant graphitic basement faults.
  • Up to four initial target areas will be evaluated.
• Murphy Lake North (MLN) Drilling Plan:
  • Drilling plans comprise approximately 1,200 metres.
  • Follows up on summer 2025 results at the Cyclone trend, where broad zones of structure and alteration were intersected over a two-kilometre strike length.
  • Targets a 1,200-metre gap in existing drilling where a lake prevents summer access.
  • Will test a potential trend parallel to and approximately 100 metres south of Cyclone, interpreted from intensely graphitic rocks and faulting intersected in the basement of MLN25-007.
• Project Locations and Context:
  • Darby: Located 10 kilometres west of Cameco's Cigar Lake mine in the eastern Athabasca basin, Saskatchewan. Last drilled in 2009. Contains multiple prospective conductive trends and historical intersections of weak uranium mineralization.
  • Murphy Lake North: Located 2.7 kilometres east of IsoEnergy's Hurricane deposit. Covers a portion of the Larocque Lake trend, hosting the along-strike extension of basement geology underlying the Hurricane deposit (Hurricane trend) and a parallel conductive trend to the south (Cyclone trend).
• Joint Venture Structure:
  • Darby and MLN are 70/30 joint ventures between Cosa Resources (operator) and Denison Mines.
  • In January 2025, Cosa entered a strategic collaboration with Denison, securing access to additional highly prospective eastern Athabasca uranium exploration projects.
• Technical Verification:
  • Historical drilling and geophysical results sourced from the Saskatchewan Mineral Assessment Database (SMAD) and confidential data supplied by Denison.
  • Verification included confirming historical drill hole collar locations via air photos and ground checking with GPS.
  • Basement and lower sandstone sections from most historical drill holes were relogged in 2024 and 2025.
  • Geochemical results for drill holes completed between 2008 and 2010 were verified via reissuance of analytical certificates by the Saskatchewan Research Council (SRC).
  • Geophysical survey grids confirmed from air photos; MLN historical geophysical surveys were re-interpreted by a consultant.
• Qualified Person:
  • Andy Carmichael, PGeo, vice-president, exploration for Cosa, has reviewed and approved the technical disclosure under National Instrument 43-101.