Orosur Mining Inc - infill drilling continues to deliver, 71.85m @ 6.13g/t Au.

·    Assays from four more holes from the Pepas MRE infill program include:

o PEP050 - 34m @ 2.33g/t Au from surface

o PEP051 - 61.3m @ 3.36g/t Au

o PEP052 - 71.85m @ 6.13g/t Au

·    El Cedro soil sampling 45% complete - first samples submitted for assay.

·    Contracts being finalised for El Pantano (Argentina) drilling - planned to commence mid-October.

London, August 26^th, 2025. Orosur Mining Inc. ("Orosur" or the "Company") (TSXV/AIM:OMI), is pleased to announce an update on the progress of exploration activities at the Company's flagship, 100% owned, Anzá Gold Project ("Project") in Colombia, and its El Pantano Gold/Silver Project ("El Pantano") in Argentina.

Anzá - Colombia

As announced on 14^th July 2025, the Company took the formal decision to commence infill drilling at its Pepas gold prospect at Anzá with the objective of moving Pepas to a NI43-101 compliant Mineral Resource Estimate ("MRE") by the end of the year.

The first several holes of this program (announced 17^th July 2025), vindicated this decision by returning exceptional widths and grades, especially hole PEP045 which returned 62.3m @ 12.76g/t Au.

The drill program has been designed in conjunction with external consultants to facilitate a MRE being calculated, with the multiple objectives of infilling previous drilling, expanding beyond current drilling to define the boundaries, and understanding the geological controls upon mineralisation and the variations in geology and grade across the deposit.

Holes will be drilled in an order that attempts to address these issues concurrently.

These four holes announced today are a continuation of this program and designed largely to infill to the required spacing to allow a MRE to be calculated to a high level of confidence. Drilling continues to return thick sequences of high-grade gold mineralisation, starting from surface or near surface.

Importantly, drilling is also providing guidance as to grade and mineralogical variation across the ore body that will allow our teams to define various metallurgical domains that will in turn form the basis of more advanced metallurgical studies that are planned to commence soon.

Table 1. Latest drill Intercepts, Pepas Prospect

Figure 2.  Plan of holes

Figure 3. Section, PEP050

Figure 4. Section PEP051, PEP051 and PEP053

El Cedro - Anzá, Colombia

The El Cedro prospect is a large gold porphyry system, located toward the south of the Anzá project, on the same granted exploration licence as the Pepas and APTA deposits.

The Company has recommenced a large ridge and spur soil sampling program that had been previously suspended due to seasonal rain and access issues.  This program is now roughly 45% complete, and it is expected that the remainder of the program should be completed by mid-October 2025.

The first batch of 40 samples from the restarted program have been submitted for assay this week, with results expected soon.

El Pantano - Argentina

The El Pantano Project is an early-stage gold/silver exploration project in Santa Cruz province, southern Argentina.

The Project comprises approximately 550km2 of contiguous licences in the prolific Deseado Massif region, roughly 45km from Anglo Gold's Cerro Vanguardia mining camp. 

The El Pantano Project is subject to an Exploration & Joint Venture ("JV") agreement ("Agreement") with private Argentinean company DESEADO DORADO S.A.S and its shareholders ("Deseado"), the details of which were announced on February 15^th 2022. The Company has earned a 51% interest in the El Pantano Project and must spend an additional US$2m in the two years from Feb 14^th, 2025, in order to earn 100% ownership.

The Company has been carrying out regional exploration at El Pantano for several years, including geological mapping, geochemical sampling, ground magnetics and induced polarisation geophysical surveys. These work programs have provided evidence suggestive of major rift-related low sulphidation epithermal system, of the type that has led to the development of major gold and silver deposits in the region.

Drill permits for El Pantano were obtained late in 2024, and the Company is now finalising drill contracts with a view to commencing drilling in mid-October 2025, the first drill program that has ever been undertaken anywhere on the property.

Between 10 and 14 diamond holes are planned for a total of approximately 3000m, targeting geological structures and geochemical/geophysical anomalies identified from previous work. Additional details will be provided once more precise timing is finalised.

The area is very remote and largely unpopulated and thus substantial effort has been required to plan and develop the necessary camp and access infrastructure for a drilling program of this size.

The Deseado Massif is a major gold producing area in Argentina and thus some necessary downstream infrastructure exists in the region. In particular, an international laboratory company has a fire assay facility in the regional town of Perito Moreno and thus a short assay turnaround time (for gold and silver) is anticipated.

Orosur CEO Brad George commented:

"Pepas remains on track and the high bar set by the early holes continues to be cleared on a regular basis. In the meantime, we are excited to be getting close to opening a second drilling front on our El Pantano project in Argentina. Early stage, but this is elephant country, and we like what we have seen thus far".

Colombia - ANZÁ Project ("Project")

The Anzá Project is now 100% owned by the Company following completion of a Share Purchase Agreement ("SPA"), announced 28^th November 2024, whereby the Company purchased all of the shares of its previous JV partner; Minera Monte Aguila ("MMA").

The Project, which is located 50km west of Medellin, is easily accessible and boasts excellent infrastructure including water, power and communications as well as a large exploration camp. 

From September 2018 to November 2024, the Anzá Project was under the control of its previous JV partner MMA, itself a 50/50 venture between the world's two largest gold miners, Agnico Eagle Mines and Newmont Mining.

Prospects

The Company is currently focussed on three prospects within the Anzá Project - Pepas, APTA and El Cedro. All three prospects are within the same granted exploration title that is broken into two, non-contiguous pieces (Figure 2).

Drilling is currently being undertaken at the Pepas prospect in the northern extent of the Anzá Project (pre-acquisition) over 10km north of the central base camp at APTA. In parallel, mapping and sampling is being undertaken over the El Cedro porphyry system in the south of the project area.

Figure 5. Main prospects, licences pre-MMA acquisition

Holes Drilled post MMA Transaction

38 holes have been drilled at Pepas since the MMA Transaction in November 2024.

Assay results are tabulated below.

Table 2.  Results to date, post MMA Transaction

For further information, visit www.orosur.ca, follow on X @orosurm or please contact:

Orosur Mining Inc

Louis Castro, Executive Chairman,

Brad George, CEO

[email protected]

Tel: +1 (778) 373-0100

SP Angel Corporate Finance LLP - Nomad & Joint Broker

Jeff Keating / Jen Clarke / Devik Mehta

Tel: +44 (0) 20 3470 0470

Turner Pope Investments (TPI) Ltd - Joint Broker

Andy Thacker/James Pope
Tel: +44 (0)20 3657 0050

Flagstaff Communications and Investor Communications

Tim Thompson
Mark Edwards
Fergus Mellon

[email protected]

Tel: +44 (0)207 129 1474

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014 ('MAR') which has been incorporated into UK law by the European Union (Withdrawal) Act 2018. Upon the publication of this announcement via Regulatory Information Service ('RIS'), this inside information is now considered to be in the public domain.

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.

Drill Hole Details - Pepas prospect 2022/2024 Programme*

*  Coordinates WGS84, UTM Zone 18

About Orosur Mining Inc.

Orosur Mining Inc. (TSXV: OMI; AIM: OMI) is a minerals explorer and developer currently operating in Colombia, Argentina and Nigeria.

About the Anzá Project

Anzá is a gold exploration project, comprising three exploration licences, and a large number of licence applications, totalling 399km2, in the prolific Mid-Cauca belt of Colombia.

The Anzá Project is currently wholly owned by Orosur via its subsidiaries, Minera Anzá S.A. and Minera Monte Aquila S.A.S.

The project is located 50km west of Medellin and is easily accessible by all-weather roads and boasts excellent infrastructure including water, power, communications and large exploration camp.

Qualified Persons Statement

The information in this news release was compiled, reviewed, verified and approved by Mr. Brad George, BSc Hons (Geology and Geophysics), MBA, Member of the Australian Institute of Geoscientists (MAIG), CEO of Orosur Mining Inc. and a qualified person as defined by National Instrument 43-101.

Orosur Mining Inc. staff follow standard operating and quality assurance procedures to ensure that sampling techniques and sample results meet international reporting standards.

Drill core is split in half over widths that vary between 0.3m and 2m, depending upon the geological domain. One half is kept on site in the Minera Anzá core storage facility, with the other sent for assay.

Industry standard QAQC protocols are put in place with approximately 10% of total submitted samples being blanks, repeats or Certified Reference Materials (CRMs).

Samples for holes PEP-001 to PEP-011 were sent to the Medellin preparation facility of ALS Colombia Ltd, and then to the ISO 9001 certified ALS Chemex laboratory in Lima, Peru.

Samples from PEP-012 onwards are sent to Medellin laboratory of Actlabs for preparation and assay.

30 gram nominal weight samples are then subject to fire assay and AAS analysis for gold with gravimetric re-finish for overlimit assays of >5 g/t.  ICP-MS Ultra-Trace level multi-element four-acid digest analyses may also undertaken for such elements as silver, copper, lead and zinc, etc.

Gold intersections are reported using a lower cut-off of 0.3g/t Au over 3m.

Intersections are quoted as downhole thicknesses.  True thicknesses are unknown.

Forward Looking Statements

All statements, other than statements of historical fact, contained in this news release constitute "forward looking statements" within the meaning of applicable securities laws, including but not limited to the "safe harbour" provisions of the United States Private Securities Litigation Reform Act of 1995 and are based on expectations estimates and projections as of the date of this news release.

Forward-looking statements include, without limitation, the continuing focus on the Pepas prospect, the exploration plans in Colombia and the funding of those plans, and other events or conditions that may occur in the future. There can be no assurance that such statements will prove to be accurate. Actual results and future events could differ materially from those anticipated in such forward-looking statements. Such statements are subject to significant risks and uncertainties including, but not limited to, those described in the Section "Risks Factors" of the Company's MD&A for the year ended May 31, 2024. The Company's continuance as a going concern is dependent upon its ability to obtain adequate financing, to reach profitable levels of operations and to reach a satisfactory closure of the Creditor´s Agreement in Uruguay. These material uncertainties may cast significant doubt upon the Company's ability to realize its assets and discharge its liabilities in the normal course of business and accordingly the appropriateness of the use of accounting principles applicable to a going concern. The Company disclaims any intention or obligation to update or revise any forward-looking statements whether as a result of new information, future events and such forward-looking statements, except to the extent required by applicable law.