Orosur Mining Inc – Pepas Advancing

• First two holes at Pepas North intersect halo.
• Preliminary technical studies commencing at Pepas.
• Highly anomalous soil geochemistry at El Cedro

London, May 28th 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 Anzá Project ("Project") in Colombia.

Colombia - ANZÁ Project

Figure 1. Mid-Cauca Belt

Prospects

Figure 2. Main prospects, licences pre-MMA acquisition

Pepas and North Pepas Prospects

After completion of the transaction to buy MMA, the Company restarted drilling at Pepas in late-November 2024.

North Pepas is an area several hundred metres north of Pepas where anomalous rock chip and soil geochemistry has indicated a zone of interest.

Figure 3. Plan of holes

Drilling at Pepas, post transaction, has largely concentrated on a small central core, where a body of high-grade gold mineralisation is being defined from surface.

Hole PEP033 was drilled at the southern extent of Pepas, to gradually extend mineralisation in this direction. A thick intersection of high-grade mineralisation (21.3m @ 5.88 g/t Au) was identified from surface, suggesting potential for extension of Pepas toward the south that will require follow-up.

Hole PEP034 was drilled internal to the existing Pepas mineralised body, but orthogonal to previous drilling, and sub parallel to the Tesorito South fault, to test continuity of mineralisation from section to section and to assist in future resource modelling. A thick intersection of extremely high-grade mineralisation (59m @ 10.15g/t Au) was identified, adding substantially to the geological understanding of the Pepas body.

Hole PEP035 was drilled in the centre of Pepas, but toward the west, outside the previous mineralised envelope, to test the depth extension of previous surface mapping. The positive response from this hole (11.4m @ 2.71g/t Au) has opened up the potential for additional extensions in this direction.

Pepas North was identified as an area of potential several hundred metres to the north of Pepas, by virtue of a number of highly anomalous rock chip and channel samples.

However, these samples, while highly anomalous, contained little geological or orientation contextual information, and thus initial drilling here was unguided.

Two holes PEP036B and PEP037 were drilled as a scissor pair underneath previously defined geochemical anomalies.

Both holes intersected thick sequences of highly altered and silicified tuffs, with moderate gold mineralisation similar in nature to the lower grade halo zones identified around Pepas to the south. This is potentially suggestive that these holes may be marginal to a more mineralised system. Both also intersected numerous structurally complex zones, with some indication of having been drilled sub-parallel to the controlling strike.

A third hole, PEP038 has been collared orthogonal to these first two holes to provide additional structural and lithological information. Once complete, the rig will move back to Pepas, to allow time for full multi-element geochemical analysis to be completed on these three holes that, in conjunction with airborne magnetics and surface sampling, may be of assistance in vectoring and targeting of later exploration and drilling activities.

Drill intersections for these most recent five holes are as follows:

Table 1. Latest drill Intercepts, Pepas and Pepas North

Geological Modelling and Economic Studies

Encouraged by the exceptional results at the Pepas prospect, the Company has begun the process of geological modelling and preliminary economic assessment at Pepas.

While exploration continues across several prospects at Anzá, the Company feels that the nature of the gold mineralisation thus far defined at Pepas, could, if proven, underpin a range of development options. The Company does not at this stage plan to move Pepas to a Mineral Resource Estimate ("MRE"), or to commence formal feasibility studies, but will focus on very preliminary technical studies to better understand the optionality of Pepas and to map out work programs to further explore and advance these options.

Several studies have been completed or are underway.

The Company has commissioned external consultants to carry out 3D modelling of the body of mineralisation as it currently stands at Pepas. The purpose of this work is to compare and contrast with the modelling work done by Company geologists, to determine if an MRE can be developed and if so, to formulate a drilling plan to facilitate this.

Some months ago, several samples of Pepas core were sent to a metallurgical laboratory in Canada for preliminary metallurgical testing. These sample were not representative of the entire body of mineralisation, and the testing program was very rudimentary, designed only to test for the existence of potentially deleterious elements and to carry out a basic recovery test that could be used to guide later testing. Results from this work were positive, with no deleterious element issues being identified and 88% Au recovery being achieved by simple cyanide leaching at a coarse grind of 120 microns. More substantial metallurgical studies would be required in future if the project advances.

El Cedro

Work on the area began some years ago before Orosur's tenure, when Anglo American undertook reconnaissance mapping and sampling, identifying a highly prospective gold/copper porphyry system.

Little work was then undertaken until late 2021, when the Company's previous JV partner MMA re-entered the area to carry out mapping, sampling and ground geophysics that largely confirmed Anglo American's previous work and mapped several large dioritic intrusions and associated epithermal systems.

Figure 4. El Cedro Sampling - historical and planned - over airborne magnetics

Several weeks ago, the Company commenced a large soil sampling program, planned to cover most of what was thought to be the extent of the porphyry system.

Large soil samples were to be taken at roughly 25m intervals, along ridges and spurs for ease of access and to ensure soils were residual. Samples were sent to both Medellin and Canada for assay.

The program was expected to require approximately two months to complete, but heavy rains and associated landslides have recently prevented access to the site, with thus far only 28% of the program being completed, largely on the eastern margin of the prospect. Local government crews are working to repair the roads, but it is expected that access for OMI teams may not be re-established for some weeks.

However, early assay results have been returned and show highly anomalous results over large areas along the eastern flank, with substantial areas of over 0.3 g/t Au in soils, and some samples in excess of 1 g/t Au and 0.5% Cu.

Figure 5. El Cedro soil sample assays and progress

Soil samples have been taken at the interface between the B and C soil horizons, as clays in the C horizon act as collectors for mobile metal ions. A wider area needs to be sampled to more accurately define the background levels, however these early results are considered by OMI to be highly encouraging.

Holes Drilled post MMA transaction

26 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

Orosur CEO Brad George commented:

"Pepas is moving nicely, both in terms of expanding the footprint, but also commencing examination of potential development options. In addition, while rains are hampering us at El Cedro, the initial results of high-grade soil anomalies over such a large area are very encouraging."