Private Placement for Gross Proceeds up to C$17m

NOT FOR DISTRIBUTION TO U.S. NEWS WIRE SERVICES OR DISSEMINATION IN THE UNITED STATES.

Toronto, September 17, 2025. Orosur Mining Inc. ("Orosur" or the "Company") (TSX-V/AIM:OMI) is pleased to announce that it has entered into an agreement with Red Cloud Securities Inc. (the "Agent"), to act as lead agent and bookrunner, on behalf of a syndicate of agents, together with U.K. corporate brokers Turner Pope Investments (TPI) Ltd. and with Greenwood Capital Partners Limited (together the "U.K. Brokers"), in connection with a best efforts private placement (the "Base Offering") for gross proceeds of up to C$15,000,000 from the sale of up to 44,117,647 common shares of the Company ("New Common Shares") at a price of C$0.34 (being approximately GBP 0.1809 based on a current exchange rate for GBP to CAD of 1.88) per New Common Share (the "Offering Price").

The Company has also granted the Agent the option, exercisable in full or in part, up to 48 hours prior to the Closing Date, to sell up to an additional 5,882,353 Common Shares at the Offering Price for up to an additional C$2,000,000 in gross proceeds (the "Agent's Option", and together with the Marketed Offering, the "Offering").

Subject to compliance with applicable regulatory requirements and in accordance with National Instrument 45-106 - Prospectus Exemptions ("NI 45-106"), the New Common Shares that may be sold in Canada under the Offering will be offered for sale to purchasers in all the Provinces of Canada, except for Quebec, pursuant to the listed issuer financing exemption under Part 5A of NI 45-106, as amended by Coordinated Blanket Order 45-935 - Exemptions from Certain Conditions of the Listed Issuer Financing Exemption (the "Listed Issuer Financing Exemption") New Common Shares issued under the Listed Issuer Financing Exemption will not be subject to a hold period under Canadian securities legislation. New Common Shares issued under the Offering may also be offered for sale to purchasers outside of Canada, including but not limited

The Offering is scheduled to close on or around September 30, 2025 (the "Closing Date"), or such other date as the Company and the Agent may agree (being no later than October 17, 2025) and is subject to certain conditions including, but not limited to, receipt of all necessary approvals including the approval of the TSX Venture Exchange ("TSX-V") and admission to the AIM Market of London Stock Exchange plc ("AIM").

The Offering will allow the Company to make use of its joint listing on the TSX-V and AIM to broaden its shareholder base, including institutional investors in Canada, the UK and certain other foreign jurisdictions, and is expected to improve the liquidity of the Common Shares.

There is an offering document (the "Offering Document") related to the Offering in Canada that can be accessed under the Company's profile at www.sedarplus.ca and on the Company's website at www.orosur.ca. Prospective investors in Canada should read the Offering Document before making an investment decision.

The UK Placing

The element of the Offering which shall be undertaken by the UK Brokers in the UK, shall be carried out by way of a placing ("Placing") to institutional and other eligible investors. The Company and the UK Brokers have today entered into a placing agreement with the Company under which, on the terms and subject to the conditions set out in the placing agreement, the UK Brokers, as agents for and on behalf of the Company, have agreed to use their respective reasonable endeavours to procure placees in the UK for the New Common Shares at the Offering Price. The Placing is not being underwritten by the UK Brokers or any other person.

The timing of the closing of the book and allocations are at the discretion of the UK Brokers and the Agent, in consultation with the Company. Details of the total number of New Common Shares, together with any new Common Shares which may be issued pursuant to the Agent's Option (together "Offer Shares"), will be announced as soon as practicable after the close of the Offering via the Result of Placing Announcement.