Sienna Resources Enters into Joint Venture Agreement to Test the Deep Basin Lithium Brine Discovery Potential in Clayton Valley, Nevada

Vancouver, British Columbia--(Newsfile Corp. - January 28, 2026) - Sienna Resources Inc. (TSXV: SIEN) (OTCID: SNNAF) (WKN: A418KR) (the "Company" or "Sienna") is pleased to announce that it has entered into a joint venture agreement ("JV") with Cruz Battery Metals Corp. ("Cruz") and Adelayde Exploration Inc. ("Adelayde") to explore the deep basin lithium brine potential in Clayton Valley, Nevada. The 115 mineral claims comprising the 2,300-acre JV land package are all located within, and completely surrounded by, SLB's (formerly Schlumberger) and Pure Energy Minerals' lithium deposit (see map below). Clayton Valley, Nevada is home to the only long-established producing lithium brine basin in the U.S., Albemarle's Silver Peak lithium brine mine, which extracts lithium from subsurface brines. It has been the sole U.S. producing lithium brine operation since the 1960's.

Clayton Valley Lithium Map

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Jason Gigliotti, President of Sienna, states, "Lithium prices have been exploding in the past six months, up over 150 percent according to TradingEconomics.com. When you couple this with all-time highs in gold and silver (Kitco.com), there is a clearly improving investor appetite for junior mining stocks, as witnessed by the historic high volumes on the TSX Venture Exchange in the past month especially. Management feels this is a great strategic move to consolidate this land package, as it is the only group of claims located directly inside the only lithium brine basin in production in the USA. By consolidating this significant footprint into one block, this becomes much more appealing for potential larger partners and opens up more drilling locations with access to reach the deepest sections of brine formations in Clayton Valley. This is a win-win for all involved, and we look forward to getting activities started as lithium prices are at multi-year highs. With just over 40 million shares outstanding and fully cashed up, management is very optimistic about Sienna's leverage to any meaningful discovery on any of its major projects."

Key terms of the Joint Venture Agreement:

This binding letter agreement (this "Agreement") sets out the principal terms of a contractual joint venture (the "Joint Venture") among Adelayde Exploration Inc. ("Adelayde"), Sienna Resources Inc. ("Sienna") and Cruz Battery Metals Corp. ("Cruz" and collectively with Adelayde and Sienna, the "Parties"), whereby each Party has agreed to share in the costs, expenses, liabilities and benefits of the joint exploration and development of the mineral claims that are prospective for lithium.

• Initial Contributions and Profit Sharing: Each Party, through their respective affiliates, will continue to hold legal title to their respective mineral claims that comprise the Project as set out in Schedule A but agrees to hold such legal title for the benefit of the Joint Venture, with each Party holding a one third beneficial interest in each mineral claim until termination of or exit from the Joint Venture in accordance with the terms hereof.

• Each Party agrees to work and collaborate together to advance the exploration and development of the Project. If the Parties unanimously agree on any exploration and development programs, each Party will contribute one third of such costs and will be entitled to one third of any benefits. Similarly, each Party will be responsible for one third of any liabilities of the Project.

• Each Party will have the right to exit or terminate its participation in the Joint Venture with 30 days' written notice to the other Parties, following which such exiting Party will no longer be entitled to any benefit, cost, expense, or liability of the Joint Venture from that date going forward. Following the end of the notice period, the mineral claims of such exiting Party as set out in Schedule A will be deemed to be removed from the Joint Venture.

• Definitive Agreement. Following the creation of the Joint Venture by signing this Agreement, the Parties may elect to further develop and memorialize the terms of the Joint Venture by entering into a definitive agreement and structuring the Joint Venture through a special purpose vehicle (the "JV Entity") and transferring ownership of the mineral claims to the JV Entity (whether in the form of a unanimous shareholders agreement, limited partnership agreement, joint venture agreement, co-ownership agreement of some other form of agreement) (the "Governing Agreement"; and, together with the contribution agreements, the "Definitive Agreements"). The Definitive Agreements shall include the terms summarized in this Agreement and such other representations, warranties, conditions, covenants, indemnities, and other terms as are customary for transactions of this nature and not inconsistent with this Agreement.

Please click here to view the completed Joint Venture Agreement.

Qualified Person:

The technical contents of this release were reviewed and approved by Frank Bain, PGeo, independent to the Company and qualified person as defined by National Instrument 43-101

About Sienna

Sienna's primary focus is on its lithium assets in Nevada which include the 100% owned, 1,828-acre "Elko Lithium Project" & the 1,231-acre "Cave Creek Lithium Project" both located in Elko County, Nevada, directly bordering and surrounded by Surge Battery Metals' (NILI) "Nevada North Lithium Project" which is the highest-grade lithium clay deposit in the USA. In Clayton Valley, Nevada, Sienna has the "Deep Basin Lithium Brine Project" which has access to some of the deepest parts of the only lithium brine basin with production in the USA. In Saskatchewan, Sienna has the 31,718-acre Stonesthrow project, prospective for gold, silver and copper directly beside Ramp Metals Inc.'s (RAMP) Rottenstone Project.

"Jason Gigliotti"PresidentSienna Resources Inc.

Forward-Looking Statements

This news release contains forward-looking statements, including statements regarding the Company's plans to recommence operations, anticipated activity levels, market conditions, and future exploration and development activities. Forward-looking statements are subject to known and unknown risks, uncertainties, and other factors that may cause actual results or events to differ materially from those expressed or implied by such statements. These risks include, but are not limited to, fluctuations in commodity prices, exploration and development risks, regulatory approvals, market conditions, and the availability of financing. Readers are cautioned not to place undue reliance on forward-looking statements. The Company undertakes no obligation to update forward-looking statements except as required by applicable securities laws.

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