High grades continue Pepas, El Cedro prospectivity

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

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

Prospects

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