Orosur Mining Inc - High grades continue at Pepas, El Cedro prospectivity developing.

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

o PEP054 - 20.6m @ 2.01g/t Au

o PEP055 - 47.25m @ 15.25g/t Au

o PEP056 - 22.5m @ 1.64g/t Au

o PEP057 - 7.45m @ 3.05g/t Au and 17.1m @ 5.47g/t Au --

o PEP058 - 34.85m @ 3.24g/t Au

·    El Cedro soil program producing exceptional results.

London, September 9th, 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.

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.

These six holes announced today are a continuation of this program and designed largely to infill to the required spacing to allow an MRE to be calculated to a high level of confidence, and to define and understand the nature of the ore body margins and mineralising controls. 

Results from these holes continue to firm up the Pepas orebody and provide better definition of the nature of the thick, high-grade mineralisation. Recent results are largely as expected in terms of the grade distribution across Pepas. However, PEP055 unexpectedly intersected an extremely high-grade vein at a downhole depth of only 30m, well beyond the grades that have thus far been encountered. While only narrow (1.9m downhole width), this vein could be significant, and more work will be required to understand its extent and thus its geological and MRE significance.

The MRE infill drill program is ahead of schedule, and subject to a mid-program review, could be completed by late October 2025.  Once complete, the rig will then move back to exploration, either around Pepas, or at the APTA prospect to better understand the newly evolving geological model there. This decision will be made in coming weeks.

A comprehensive metallurgical test program is currently being developed for Pepas, with discussions underway with several laboratories in South and North America.  These plans are hoped to be finalised soon, and it is anticipated that one or two wider diameter (PQ) metallurgical holes will be required to provide the necessary weight of material for testing.

Table 1. Latest drill Intercepts, Pepas Prospect

** see section below on coarse gold

Figure 1.  Plan of holes

Figure 2. Section, PEP054, 055

Figure 3. Section PEP056, 057, 058, 059

Coarse Gold - PEP055

The quoted composite assay result from PEP055 of 47.25m @ 15.25g/t Au has been influenced by two consecutive high-grade samples across 1.9m in which visible gold was noted in core. These two consecutive samples returned 465.71g/t Au and 122.74g/t Au respectively. Outside these two samples, grades assayed were largely in line with adjacent holes.

The Company feels that these two samples represent a real, and very high-grade vein, but are also cognisant that coarse gold has the potential to create a sampling bias if incorrect sample preparation has resulted in heterogenous distribution of gold throughout the sample.  

To assess the potential impact of this, pulps from these two samples were re-assayed twice, with reasonably consistent results (table 2). The Company is therefore confident that no significant sampling bias has occurred.  Geologically however, such high-grade samples are a statistical outlier and will require further understanding so that their impact on a MRE is accurately reflected.

Table 2. Coarse gold re-assay

El Cedro - Anzá, Colombia

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

El Cedro had been explored in cursory fashion by Anglo American, prior to Orosur taking ownership of the Project in late 2014, with additional mapping and ground geophysics then carried out by the Company's previous JV partner MMA in 2022 and 2023. 

No drilling has ever been undertaken on the prospect.

The region has sparse outcrop, but a large porphyry system had been identified and roughly defined from regional mapping and more recent airborne magnetic and radiometric data.   Several phases of soil geochemical surveys were carried out in the centre of the prospect, around a central core of potassic alteration visible from airborne radiometrics, and in nearby creeks where fresh rock had been exposed.

A large area of anomalous soils was historically sampled in the centre of the prospect with numerous high grade rock chip and channel samples of between 1 and 9 g/t Au in surrounding creeks in later stage polymetallic veins (Figure 4).

To better define the scope and nature of El Cedro, the Company recently commenced a wider scale ridge and spur soil sampling program over the entire extent of what is thought to be the porphyry system. Being rugged terrain, sampling was limited to ridges and spurs to ensure that sampled material is residual and insitu.

Figure  4. El Cedro prospect- previous sampling (Anglo and MMA) and sampling plan

After a brief pause due to limited access during the wet season, this program has recommenced and is now approximately 65% complete.

Figure 5. Orosur soil sampling, El Cedro - progress

Gold assay results thus far are highly encouraging with large areas of over 0.3g/t Au and at times over 1g/t Au being identified in soils and saprolite around a central core.

Geological mapping being undertaken in conjunction with the soil program is also now better defining the porphyry system and the associated vein systems. Base metals associations have also been noted in outcrop, however, base metal assays require a different assay method not available in Colombia and these will require several weeks to be returned.

The Company feels the ongoing work program is showing El Cedro as a complex and highly prospective gold porphyry system.  Once this current program is complete in coming weeks, all data will be compiled with a view to planning the next phase of work, which could involve drilling.

Orosur CEO Brad George commented:

"The Anza Project continues to develop and broaden in scope. Pepas is progressing toward MRE as planned, but the results at El Cedro are showing this licence has much more to give".

Colombia - ANZÁ 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 5)

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 6. Main prospects, licences pre-MMA acquisition

Holes Drilled post MMA Transaction

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

Assay results are tabulated below.

Table 3.  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, 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 2022/2025 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.