Vancouver, British Columbia--(Newsfile Corp. - June 4, 2026) - Onyx Gold Corp. (TSXV: ONYX) (OTCQX: ONXGF) ("Onyx" or the "Company") is pleased to report new drill results from its fully-funded 110,000-meter drill program (the "Program") at the 100%-owned Munro-Croesus Project ("Munro-Croesus" or the "Project"), located 75 km east of Timmins, Ontario (Figure 4).

Results from 19 drill holes continue to expand the rapidly growing Argus gold system, where drilling has now outlined mineralization over approximately 1.4 km of strike length and more than 500 m vertically, while remaining open in multiple directions.

Today's results include further expansion drilling at Argus Main ("Argus Main"), where broad zones of near-surface bulk-tonnage style gold mineralization continue to grow both laterally and at depth. Drilling is also continuing to define higher-grade plunging zones associated with northeast-trending structures similar to those observed at Argus North, located approximately 600 m to the northwest. The latest drilling also further expands the emerging Argus West Zone ("Argus West") along the recently identified Argus Fault, reinforcing the Company's view that the Argus area may represent a much larger mineralized system than originally recognized.

The Program is increasingly demonstrating that northeast-trending structural corridors, including the Argus Fault, are an important control on higher-grade gold mineralization. Onyx controls approximately 16 km of the Argus Fault and more than 8 km of the Pipestone Fault corridor, providing substantial exploration runway beyond the currently defined Argus Zones.

Highlights from Argus Main

• Argus Main extended to approximately 400 metres vertical depth and remains open along strike and at depth

• Broad gold intercepts continue to demonstrate excellent continuity, including:
  • 70.8 m grading 0.8 g/t Au, including 7.0 m grading 3.4 g/t Au in drill hole MC26-297
  • 95.2 m grading 0.7 g/t Au from a major 100 m down-plunge step-out in drill hole MC26-303

• Argus Main remains connected to a near-surface mineralized footprint highlighted by channel and grab samples grading between 5.2 g/t Au and 14.7 g/t Au

• Drilling continues to confirm similarities between Argus Main and Argus North, including broad mineralized envelopes surrounding higher-grade structural zones

• One drill rig remains dedicated to expanding Argus Main along plunge and at depth

"These results continue to demonstrate that Argus is evolving into a much larger mineralized system than we initially envisioned," stated Brock Colterjohn, President & CEO. "What is particularly exciting is that we are now vectoring into multiple growth directions simultaneously. Along the northeast-trending Argus Fault, which we control for approximately 16 km, drilling continues to identify new mineralized zones associated with this important structure. At the same time, the east-west Pipestone corridor, where Onyx controls more than 8 km of strike length, remains largely untested and continues to generate new targets."

"The emerging picture is one of a large-scale structural gold system with multiple mineralized zones developing along intersecting corridors, a setting that has the potential to host numerous discoveries across the property. With four drill rigs active and approximately 48,000 metres still planned for 2026, we believe we are still in the early stages of unlocking the scale of the Argus system and the greater potential of the Property."

Highlights from Argus West

• 32.7 m grading 0.5 g/t Au, in drill hole MC25-239

• 16.2 m grading 1.1 g/t Au (from surface), in drill hole MC25-241

• 35.5 m grading 0.9 g/t Au, in drill hole MC25-273, including
  • 23.4 m grading 1.2 g/t Au

• Argus West expanded to 350 m strike length by 125 m width and remains open in all directions

• Mineralization continues to track along the northeast-trending Argus Fault, a newly recognized structure now traced for approximately 16 km across the property

• Drilling supports the emerging interpretation that the Argus Fault may host multiple Argus-style mineralized centres

• Higher-grade targets associated with visible gold remain largely untested and are a priority for follow-up drilling

Update on the Argus Zones and the Program

The Company continues to execute one of the largest fully funded gold exploration programs in the Abitibi, with 159 drill holes totalling ~62,000 m to date. Assays have now been released for 114 drill holes, with approximately 48,000 m remaining to be drilled in 2026.

The primary focus of the Program remains the continued expansion of the Argus Zones, where drilling has identified two key styles of gold mineralization:

1) Steeply plunging, high-grade gold zones associated with northeast-trending fault corridors (D2 - controlling structures); and

2) Disseminated zones of low- to moderate-grade gold zones which surround and flank the high-grade intervals within the northwest-southeast trending permissive host mafic variolitic and fragmental volcanic rock stratigraphy (D1 - stratiform-style).

The Argus Zones remain open along strike, down-dip, and down-plunge, with mineralization also projecting to the near-surface in multiple locations. Notably, the higher-grade zones such as Argus North and Argus Main show an apparent periodicity of 400 m along strike within the host mafic variolitic volcanic unit, coinciding with the intersection with northeast-trending mineralizing structures.

Ongoing geological and geophysical work continues to refine the controls on gold mineralization along the Pipestone Fault corridor, where Onyx controls more than 8 km of strike length in one of the most prospective yet underexplored portions of the Timmins gold camp.

A 420 line-km high-resolution drone magnetic survey was recently completed to refine drill targets and northeast controlling structures across the Argus Zones and the greater Pipestone Fault corridor.

The Company is fully funded with approximately $20 million in cash.

The Geological Setting of the Argus Zones

The Argus Zones are located on the western half of the Munro-Croesus Project, approximately 3 km northwest of the historic Croesus Gold Mine and immediately north of the regional Pipestone Fault, a major structural corridor host to many of the significant gold deposits in the Timmins camp (Figure 1). Following a multi-year consolidation effort, Onyx now controls over 8 km of strike extent of the Pipestone Fault, most of which remains undrilled or has not seen any modern exploration. Gold mineralization is hosted within volcanic rocks of the Kidd-Munro assemblage across all Argus Zones.

The Argus North Zone is situated 150 m north of the Pipestone Fault and is distinguished by both broad zones (50 m to over 100 m) of +1 g/t Au mineralization containing wide zones of higher-grade mineralization (+5 g/t Au). The higher-grade sub-intervals are associated with zones of strong albitization and silicification, pyritic stringers, and localized porphyritic intrusions within mafic variolitic basalt and volcanic breccias cut by dominant moderate to steeply dipping, northeast-trending faults and associated fractures. This combination of host lithology, alteration and structural preparation is interpreted to be a key control on gold deposition. The discovery hole, MC24-163, was reported last year, and returned 69.6 m grading 3.4 g/t Au, including
34.5 m grading 5.4 g/t Au and 9.5 m grading 13.9 g/t Au (see Company news release dated April 10, 2025).

The Argus Main Zone lies ~100 m south of Argus North and represents a separate, broad east-west trending, 900 m x 200 m near-surface bulk-tonnage gold target. The best surface expression of the Argus Main Zone is stripped of overburden and consists of 10 grab and channel samples grading between 5.2 g/t Au and 14.7 g/t Au, within a 35 x 30 m area. Gold mineralization is associated with mafic variolitic volcanic flows that are strongly albite- and silica-altered and cut by east-northeast-trending pyritic veinlets within a broader halo of carbonate alteration and local development of specular hematite. Highlights from past drilling include 63.3 m grading 1.0 g/t Au, including 17.4 m grading 2.2 g/t Au in MC24-166 (see Company news release dated June 17, 2024), 62.8 m grading 0.8 g/t Au within 136.0 m grading 0.5 g/t Au in MC22-110 (see Company news release issued dated May 9, 2022), 59.7 m grading 1.0 g/t Au, including 18.4 m grading 2.0 g/t Au in MC25-255 (see Company news release issued dated February 18, 2026) and 27.6 m grading 1.0 g/t Au in MC23-140, and Figures 1, 2, and 3).

The Argus West Zone is located ~250 m west of Argus North, along the recently delineated 'Argus Fault', a key northeast-trending, moderately-to-steeply NW-dipping structure that appears to play an important role as a locus for gold mineralization. Drill hole MC25-213 returned 21.2 m grading 2.1 g/t Au (with local visible gold) starting at 9.8 m downhole within strongly albite-altered mafic variolitic volcanics with a moderate crackle brecciation, and fine-grained disseminated to fracture-controlled pyrite in the structural hanging wall to the Argus Fault (see Company news release dated December 3, 2025). Drill hole MC25-199, located a further 180 m to the southwest, intersected 14.0 m grading 1.0 g/t Au hosted by fine-grained metasedimentary rocks of the Porcupine Group, in the structural footwall to the Argus Fault.

Discussion of Argus Main Drill Results

The key results include a further two (2) drill holes from the emerging Argus Main target area, where drilling continues to define broad zones of gold mineralization associated with the aforementioned northeast-trending structures containing higher-grade intervals similar to those seen at Argus North, located approximately 600 metres to the northwest.

The two drill holes reported today from Argus Main follow up on the two discovery holes, MC26-267 and MC26-270, which intersected 99.5 m of 1.2 grams per tonne gold ("g/t Au") and 77.2 m grading 1.3 g/t Au in MC26-270, respectively (See Company news release dated March 31, 2026).

• Drill hole MC26-297 was designed to test the Argus Main zone 40 m up-dip from hole MC26-270. The hole intersected two mineralized zones which appear to correlate to the upper and lower zones intersected in hole MC26-270.

• Drill hole MC26-303 was designed to test the Argus Main zone 100 m down-dip of hole MC26-267. The hole also intersected upper and lower zones.

Highlights from Argus Main

• 13.4 m grading 1.4 g/t Au (Upper Zone - from 53.1m downhole), in drill hole MC26-297, including
  • 7.3 m grading 2.1 g/t Au

• 70.8 m grading 0.8 g/t Au (Middle Zone - from 244.0 m downhole), in drill hole MC26-297, including
  • 12.0 m grading 1.9 g/t Au, including
    • 0.9 m grading 7.3 g/t Au, and including
  • 7.0 m grading 3.4 g/t Au, including
    • 3.5 m grading 6.3 g/t Au
      • 1.8 m grading 8.6 g/t Au

• 15.3 m grading 0.5 g/t Au (Lower Zone - from 407.4 m downhole), in drill hole MC26-297

• 95.2 m grading 0.7 g/t Au (from 557.5 m downhole), in drill hole MC26-303, including
  • 5.4 m grading 1.9 g/t Au, including
    • 1.0 m grading 6.7 g/t Au, and including
  • 9.9 m grading 1.1 g/t Au, including
    • 7.5 m grading 1.4 g/t u

The Argus Main zone has been defined to surface where high-grade surface channel and grab samples grade between 5.2 g/t Au and 14.7 g/t Au over a 35 x 30 m area, and to approximately 400 m vertical depth.

The style of alteration and mineralization at Argus Main is analogous to Argus North with moderate to strong albite-carb-silica, fracturing with local development of crackle breccia, hosted within mafic variolitic to pillowed volcanics, with 1-3% fine pyrite.

The Argus Main zone remains open along strike and at depth and one drill rig is currently dedicated to systematic expansion drilling along the up and down the plunge of the zone.

Details for drill hole assays reported in this news release are shown in Figures 1/2/3 and Table 1.

Discussion of Argus West Drill Results

Drilling at the Argus West zone has focused on testing the Argus North plunging shoot to the west-northwest. The results from the 17 drill holes reported have now expanded Argus West to 350m strike x 125m width with an orientation parallel to, and in association with, the northeast-trending, northwest-dipping Argus Fault. The Argus West zone remains open in all directions.

Highlights from Argus West

• 32.7 m grading 0.5 g/t Au (from 72.0 m downhole), in drill hole MC25-239, including
  • 4.0 m grading 2.5 g/t Au, including
    • 1.0 m grading 7.1 g/t Au

• 16.2 m grading 1.1 g/t Au (from surface at 6.3 m downhole), in drill hole MC25-241, including
  • 8.2 m grading 1.8 g/t Au, including
    • 4.2 m grading 2.4 g/t Au

• 1.2 m grading 8.8 g/t Au (from 226.3 m downhole), in drill hole MC26-257

• 35.5 m grading 0.9 g/t Au (from 55.0 m downhole), in drill hole MC25-273, including
  • 23.4 m grading 1.2 g/t Au, including
    • 3.6 m grading 5.6 g/t Au, including
      • 1.1 m grading 11.6 g/t Au

The apparent NE-SW orientation of the expanded Argus West mineralized zone validates the current working theory that the mineralization is being controlled by the northeast-trending, moderately northwest-dipping Argus Fault, dipping moderately to the NW. Mineralization is hosted in both the hanging wall and footwall of the Argus Fault in variolitic basalt to the northwest and metasedimentary rocks to the southeast. Drilling will now focus on defining a higher-grade core or plunge zone related to the higher-grade intersection with visible gold in hole MC25-213 (21.2 m grading 2.1 g/t Au incl. 14.0 m grading 3.0 g/t Au) (See Company news release dated December 3, 2025).

The Argus West zone has been defined for 350 m along strike and over a width of 125 m and remains open on all directions.

Current Understanding of Argus Zones

The Argus Zones continue to demonstrate strong continuity of gold mineralization across multiple zones and host lithologies over a total strike length of approximately 1,400 m and a vertical extent exceeding 500 m. The zones remain open along strike, at depth, and down-plunge, with several areas showing potential to extend mineralization toward surface.

Drilling completed to date is increasingly supporting the Company's interpretation that northeast-trending structures play a key role in controlling higher-grade gold mineralization. These structures remain largely untested across the broader Pipestone corridor, which Onyx controls 8 km of prospective strike length. Management believes the combination of favourable host rocks, large-scale structural preparation, and emerging high-grade plunging zones highlights the potential for additional discoveries across the Project.

Table 1 - Significant Assay Results for Argus North Drill Holes Reported in this Release

*Intersections are reported as drilled width; true width is 60-90% of drilled width

Table 1 (Continued)

Table 1 (Continued)

Figure 1 - Plan Map Highlighting Argus Zone Drill Holes Reported in this Release

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Figure 2 - Cross-Section Highlighting Argus Main Drill Holes Reported in this Release - Looking Northeast - 50m window

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Figure 3 - Longitudinal Section Highlighting Drill Holes Reported in this Release - Looking North

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Figure 4 - Location of the Munro-Croesus Gold Project, Ontario

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The Munro-Croesus Project

The Munro-Croesus Project is located along Highway 101 in the heart of the Abitibi greenstone belt, Canada's premier gold mining jurisdiction (Figure 4). This large, 100%-owned land package includes the past-producing Croesus Gold Mine, which yielded some of the highest-grade gold ever mined in Ontario. Extensive land consolidation since 2020 has unified the patchwork of patented and unpatented mining claims surrounding the Croesus Gold Mine into one coherent package and enhanced the project's exploration potential.

The Project covers 112 km² of highly prospective geology within the influence of major gold-bearing structural breaks. Bulk-tonnage gold deposits located in the immediate region include the Fenn-Gib gold project being developed by Mayfair Gold Corp., and the Tower Gold Project being developed by STLLR Gold Inc.

About Onyx Gold

Onyx Gold Corp. (TSXV: ONYX) (OTCQX: ONXGF) is a Canadian exploration company focused on unlocking district-scale gold opportunities in two of the country's most prolific and proven mining jurisdictions — Timmins, Ontario, and Yukon Territory.

In the Timmins Gold Camp, Onyx controls an extensive portfolio anchored by the Munro-Croesus Property, host to the historic high-grade Croesus Mine and site of the Company's recent Argus North discovery - one of the most exciting new gold zones emerging in the camp. Complementing Munro-Croesus are two large, early-stage projects - Golden Mile, a 140 km² property situated just 9 km from Discovery Silver's multi-million-ounce Hoyle Pond Mine, and Timmins South, a 187 km² land package strategically positioned around the Shaw Dome structure, offering exceptional discovery potential.

Beyond Ontario, Onyx holds a commanding land position across four properties in Yukon's Selwyn Basin, an area rapidly gaining recognition for new gold discoveries and growing exploration investment. The Company's King Tut Property sits approximately 50 km south of Snowline Gold's Valley discovery and adjacent to Fireweed Metals' MacPass property.

Led by an experienced team with a strong track record of discovery, development, and value creation, Onyx Gold is well-funded and committed to delivering shareholder value through disciplined exploration, strategic growth, and responsible resource development.

On Behalf of Onyx Gold Corp.

"Brock Colterjohn"
President & CEO

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Additional Notes:

A table of all drill collar details and significant assay intersections can be found on the Company website at https://onyxgold.com/projects/munro-croesus-gold/.

Samples of drill core were cut by a diamond blade rock saw, with half of the cut core placed in individual sealed polyurethane bags and half placed back in the original core box for permanent storage. Sample lengths typically vary from a minimum 0.2-meter interval to a maximum 1.5-meter interval, with an average 0.5 to 1.0-meter sample length. Drill core samples were delivered by truck in sealed woven plastic bags to ALS Geochemistry laboratory facility in Timmins, Ontario for sample preparation with final analysis at ALS Geochemistry Analytical Lab facility in North Vancouver, BC, for the fire assay fusion method and inductively coupled plasma (ICP), with the photon assay method performed at the ALS Geochemistry Analytical Lab facility in Thunder Bay, Ontario. ALS Geochemistry operates meeting all requirements of International Standards ISO/IEC 17025:2017 and ISO 9001:2015

Drill core samples were crushed to 70% passing 2mm, then a representative split was taken and pulverized to 85% passing 75μm. For the RUSH portion of all drill holes, gold was determined by the photon assay method (Au-PA01) of a 500-gram crush split sample providing a true bulk reading. The photon assay method utilizes high-energy X-rays that cause excitation of atomic nuclei, allowing enhanced analysis for gold.

For all drill holes (including the RUSH mineralized portion), gold was also determined by the fire-assay fusion method (Au-AA26) of a 50-gram sub-sample with atomic absorption spectroscopy (AAS). Samples that returned values >10 ppm gold from fire assay and AAS were determined by using fire assay and a gravimetric finish. Various metals, including silver, gold, copper, lead, and zinc, were analyzed by inductively coupled plasma atomic emission spectroscopy (ME-ICP61), following multi-acid digestion. The elements copper, lead and zinc were determined by ore grade assay for samples that returned values >10,000 ppm by ICP analysis. Silver was determined by ore-grade assay for samples that returned>100 ppm.

All ALS Geochemistry sites operate under a single Global Geochemistry Quality Manual that complies with ISO/IEC 17025:2017. ALS Geochemistry follows the quality management and operational guidelines set out in the international standards ISO/IEC 17025 - "General Requirement for the Competence of Testing and Calibration Laboratories" and ISO 9001 - "Quality Management Systems".

The Company maintains a robust QA/QC program that includes the collection and analysis of duplicate samples and the insertion of blanks and standards (certified reference material).

Ian Cunningham-Dunlop, P.Eng., Executive Vice President for Onyx Gold Corp. and a qualified person ("QP") as defined by Canadian National Instrument 43-101, has reviewed and approved the technical information contained in this release.

Cautionary and Forward-Looking Statements

Forward-looking statements include predictions, projections, and forecasts and are often, but not always, identified by the use of words such as "seek", "anticipate", "believe", "plan", "estimate", "forecast", "expect", "potential", "project", "target", "schedule", "budget" and "intend" and statements that an event or result "may", "will", "should", "could" or "might" occur or be achieved and other similar expressions and includes the negatives thereof. All statements other than statements of historical fact included in this release, including, without limitation, statements regarding the potential significance of the latest results from the Argus North discovery are forward-looking statements that involve various risks and uncertainties. There can be no assurance that such statements will prove to be accurate and actual results and future events could differ materially from those anticipated in such statements. Forward-looking statements are based on a number of material factors and assumptions. Important factors that could cause actual results to differ materially from Company's expectations include actual exploration results, changes in project parameters as plans continue to be refined, results of future resource estimates, future metal prices, availability of capital, and financing on acceptable terms, general economic, market or business conditions, uninsured risks, regulatory changes, defects in title, availability of personnel, materials, and equipment on a timely basis, accidents or equipment breakdowns, delays in receiving government approvals, unanticipated environmental impacts on operations and costs to remedy same, and other exploration or other risks detailed herein and from time to time in the filings made by the Company with securities regulators. Although management of the Company has attempted to identify important factors that could cause actual results to differ materially from those contained in forward-looking statements or forward-looking information, there may be other factors that cause results not to be as anticipated, estimated, or intended. There can be no assurance that such statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements and forward-looking information. Readers are cautioned that reliance on such information may not be appropriate for other purposes. The Company does not undertake to update any forward-looking statement, forward-looking information or financial outlook that are incorporated by reference herein, except in accordance with applicable securities laws. We seek safe harbor.

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Source: Onyx Gold Corp.