O3 Mining Inc. (TSXV: OIII) (OTCQX: OIIIF) is pleased to provide additional assay results from our winter drill program on our Marban Engineering Project in Val-d’Or, Québec, Canada. In this news release, the Corporation is reporting 17 significant intercepts in nine drill holes from the Malartic H deposit drill program completed in March 2023. The Malartic H deposit consists of multiple stacked lenses covering an area of 600 metres along strike and 300 metres wide.

Highlights:

• 5.9 g/t Au over 10.1 metres in hole O3MA-23-463 at a vertical depth of 122 metres, including 53.2 g/t over 1.0 metre;
• 2.6 g/t Au over 6.9 metres in hole O3MA-22-474 at a vertical depth of 98 metres;
• 3.5 g/t Au over 7.5 metres in hole O3MA-22-477 at a vertical depth of 247 metres.

O3 Mining’s President and Chief Executive Officer, Mr. José Vizquerra commented: “These new assay results from our 2023 winter drill program substantiate the presence of thick mineralized zones at Malartic H as previously highlighted by historical drilling. These results reinforce the prospectivity of the two main shears – being the Marbenite and the Norbenite – which cut across the Marban property. We are looking forward to receiving the remaining assay results from the core samples extracted from the Malartic H deposit during our 2023 winter drill program.”

As part of the 2023 winter drill program, drill holes covered a one kilometre stretch, filling gaps covered by historic drilling in the shallow part of the Malartic H deposit to achieve an 80 metre spacing. Most of the historical drilling was completed by NioGold Mining Corp. and Aur Resources Inc., with QA/QC procedures applied and documented. Assay results reported today are from the south-eastern part of the Malartic H deposit and assay results from the central part of the Malartic H deposit are expected in the coming weeks. Once all assay results are received, O3 Mining expects to release a maiden mineral resource estimate on the Malartic H deposit by the end of the second quarter of 2023.

Malartic H is located within five kilometres of the proposed processing plant described in the current pre-feasibility study on the Corporation’s Marban Engineering Project.

Table 1: Near Surface Delineation Drill Hole Intercepts. Only intercepts above 5.0 g/t Au*m are reported, cut-off 0.3 g/t Au and above 200 metres from surface.

Table 2: Deeper Delineation Drill Hole Intercepts. Only intercepts above 5.0 g/t Au*m are reported, cut-off 1.0 g/t Au and below 200 metres from surface.

Figure 1 – Marban Property Map

Figure 2: Location of significant intercepts at Malartic H

About the Malartic H deposit

The Malartic H deposit has a recognized strike length of 600 metres, 300 metres wide and down to a vertical depth of 500 metres. The mineralized system is partially open laterally and completely open at depth. It is located about 1 kilometre to the north of the Malartic Hygrade former mine, near the hinge of a regional Z-shaped fold. More importantly the Malartic H deposit is also located between the northwestern extensions of the Marbenite and Norbenite shears, which host most of the resources of the Marban Engineering Project. At Malartic H, the two shears are northwest-trending and dipping around 70 degrees to the northeast. The deposit is hosted by an alternance of mafic and ultramafic volcanic sequence of the Jacola formation. Similar to the Hygrade area, numerous intermediate to felsic dyke systems are injected in the volcanic sequence. The mineralization occurs as disseminated pyrite with local visible gold in quartz veins and veinlets and disseminated in the host rock. Zones are spatially correlated shears within mafic volcanic units or with the intermediate to felsic dykes. All zones are roughly subparallel.

The 2023 winter drilling program on the Malartic H deposit comprises 23 drill holes totaling 6,948 metres. The parameters are listed in Table 3 for the entire program. Assays results are completely received for only 8 of those holes.

Table 3: Technical parameters of holes of the 2023 campaign on Malartic H.

For full drilling results, please see our website www.o3mining.com.

Qualified Persons

The scientific and technical content of this news release has been prepared, reviewed and approved by Mr. Sébastien Vigneau (OGQ #993), Principal Geologist of O3 Mining, who is a “qualified person” within the meaning of National Instrument 43-101 – Standards of Disclosure for Mineral Projects.

Quality Assurance/Quality Control

Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Half-core samples are shipped to Agat laboratory in Val-d’Or, Québec, and Mississauga, Ontario for assaying. The core is crushed to 75% passing -2 mm (10 mesh), a 250 g split of this material is pulverized to 85% passing 75 microns (200 mesh) and 50 g is analyzed by Fire Assay (FA) with an Atomic Absorption Spectrometry (AAS) finish. Samples assaying >10.0 g/t Au are re-analyzed with a gravimetric finish using a 50 g charge.

Commercial certified standard material and blanks are systematically inserted by O3 Mining’s geologists into the sample chain after every 18 core samples as part of the quality assurance and quality control program. Third-party assays are submitted to other designated laboratories for 5% of mineralized samples. Drill program design, QA/QC, and interpretation of results are performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices.

About O3 Mining Inc.

O3 Mining Inc., an Osisko Group company, is a gold explorer and mine developer on the road to produce from its highly prospective gold camps in Québec, Canada. O3 Mining benefits from the support, previous mine-building success and expertise of the Osisko team as it grows towards being a gold producer with several multi-million-ounce deposits in Québec.

O3 Mining is well-capitalized and owns a 100% interest in all its properties (62,000 hectares) in Québec. O3 Mining trades on the TSX Venture Exchange and OTC Markets. The Corporation is focused on delivering superior returns to its shareholders and long-term benefits to its stakeholders.