Mr. Brock Colterjohn reports

ONYX GOLD INTERSECTS ADDITIONAL HIGH-GRADE GOLD AT THE GM VEIN ON THE MUNRO-CROESUS PROJECT, ONTARIO

Onyx Gold Corp. has released additional gold results for the next 14 drill holes from its continuing, fully financed 3,000-metre spring drill program at its Munro-Croesus project in the Timmins gold camp in Ontario.

The 14 drill holes reported today were completed at the new GM Vein, located 350 metres ("m") from the past-producing Croesus Gold Mine, which yielded some of Ontario's highest-grade gold ever mined. Highlights are provided below, with key drill results in Table 1.

• Drilling continues to intersect encouraging results from the GM Vein at an average vertical depth of 50-60 m with visible gold observed in four of the 14 holes reported today (MC24-152/154/156/162).
• Drilling has now defined a higher-grade shoot plunging to the southwest and the GM Vein remains open for expansion in all directions.
• Significant assay intersections include:
  • MC24-154, a follow-up hole completed 10 m southwest from Hole MC23-132 (121.8 grams per tonne ("g/t") gold ("Au") 0.9 m - See Company press release dated December 6, 2023), returned 52.06 g/t Au over 0.5 m within a broader zone of 26.52 g/t Au over 1.0 m.
  • MC24-151, a follow-up hole completed 10 m northeast from Hole MC23-132, returned 20.44 g/t Au over 0.4 m within a broader zone of 10.97 g/t Au over 0.8 m.
  • MC24-152, a follow-up hole completed 20 m up-dip from Hole MC24-151, returned 32.31 g/t Au over 0.3 m within a broader zone of 7.68 g/t Au over 1.4 m.
  • MC24-156, a follow-up hole completed 5 m up-dip from Hole MC24-154, returned 15.52 g/t Au over 0.4 m.
• A total of 20 holes totaling 1,713 m were drilled on the GM Vein in March and April 2024. Seventeen (17) short drill holes (MC24-143 to MC24-159) were completed across the GM Vein on three 10 metre-spaced drill fences. Two additional holes (MC24-160 and MC24-162) were completed 30 m down-plunge and 30 m up-plunge from the three main fences of holes. One hole, MC24-161, was drilled to the northeast to test for the prospective carbonaceous, sulfidic "flow top" breccia, which hosts the higher-grade portion of the Croesus Vein, 350 m to the southeast.
• ~84% of drill holes (16 of 19 holes drilled to date) intersected mineralization greater than 0.5 g/t Au. Ten drill holes intersected mineralization over 10 g/t Au.
• The diamond drill rig is now testing the bulk-tonnage Argus Zone located three kilometres west of the GM Vein. The remaining program metreage will be dedicated to expanding the Argus Zone beyond its current strike length of 525 m and 200 m thickness.
• Given the encouraging results, the Program has been upsized by 10% to 3,300 m and will wind up shortly. Assay results will be released on an ongoing basis pending review and compliance with Company QA/QC protocols.

"We are very encouraged with the results from this year's spring program so far," said Brock Colterjohn, President & CEO. "Our drilling efforts have successfully defined a higher-grade shoot, and the GM Vein remains open for expansion in all directions. We look forward to further expanding this high-grade lens and exploring for similarly plunging zones with future drill programs."

"We are now drilling over at the bulk-tonnage Argus zone target, with the objective of extending the zone further to the west. We've expanded the program by 10% to 3,300 metres, reflecting the positive results and our confidence in the project's prospects. Our commanding land position and wealth of opportunities for new discoveries provides the potential for Onyx to become the go-to explorer in the Timmins Camp. We are looking forward to reporting further assays as they become available."

Highlight Assay Results for GM Vein

• 26.52 g/t Au over 1.0 m, including 52.06 g/t Au over 0.5 m in hole MC24-154
• 7.68 g/t Au over 1.4 m, including 32.31 g/t Au over 0.3 m in hole MC24-152
• 10.97 g/t Au over 0.8 m, including 20.44 g/t Au over 0.4 m in hole MC24-151
• 15.52 g/t Au over 0.4 m in hole MC24-156
• 4.40 g/t Au over 0.8 m in hole MC24-162
• 2.62 g/t Au over 0.8 m in hole MC24-155
• 2.45 g/t Au over 0.3 m in hole MC24-153
• 1.77 g/t Au over 1.2 m in hole MC24-150
• 1.75 g/t Au over 2.0 m in hole MC24-158

Discussion of GM Vein Results

The GM Vein was first discovered in the 2023 fall drill program when drill hole MC23-132 intersected a 30 cm wide quartz vein with abundant visible gold that returned 363 g/t Au over 0.3 m. This intersection represents the single highest assay in the Company's drill hole database for the Project. The high-grade vein occurs within a broader zone of mineralization averaging 121.8 g/t Au over 0.9 m and was intersected approximately 60 m vertically below surface. This discovery represents an entirely new bonanza-grade quartz vein in a geological setting comparable to the mined-out, very high-grade Croesus vein, located 350 m to the southeast, along the prospective Croesus pillowed mafic volcanic flow.

A total of 20 holes totaling 1,713 m were drilled on the GM Vein in March and April 2024. Seventeen (17) short drill holes (MC24-143 to MC24-159) were completed on three 10 metre-spaced drill fences around hole MC23-132, two holes (MC24-160 and MC24-162) were drilled 30 m down-plunge and 30 m up-plunge respectively, and one hole, MC24-161, was drilled to the northeast to test for the prospective carbonaceous, sulfidic "flow top" breccia, which hosts the higher-grade portion of the Croesus Vein, 350 m to the southeast.

Results for the first six holes on the GM Vein were reported in mid-April and included 51.27 g/t Au over 0.5m in hole MC24-147 (See Company press release dated April 17, 2024). Results reported today are from the next 14 holes (MC24-149 to 162) and the drilling continues to intersect encouraging results from the GM Vein over widths of 0.3 m to 2.0 m and at an average vertical depth of 50 to 60 m. Visible gold was observed in four of the 14 holes reported today (MC24-152/154/156/162) and continues to be associated with thin black wavy stylolites within the quartz-carbonate vein. Drilling has now defined a higher-grade shoot plunging to the southwest and the GM Vein remains open for expansion in all directions.

Highlights today include: 26.52 g/t Au over 1.0 m including 52.06 g/t Au over 0.5 m in hole MC24-154, 10.97 g/t Au over 0.8 m including 20.44 g/t Au over 0.4 m in hole MC24-151, 7.68 g/t Au over 1.4 m including 32.31 g/t Au over 0.3 m in hole MC24-152, and 15.52 g/t Au over 0.4 m in hole MC24-156. Figure 3 and Figure 4 show drill hole locations for the holes reported herein, and Table 1 shows significant assay intersections.

Discussion of the 2024 Spring Drill Program

The 3,000 m Program initially focused on the GM Vein with 50% of the planned metres dedicated to expanding the known high-grade gold mineralization around drill hole MC23-132 by determining a potential plunge control on the gold "shoots" and identifying new, repeated "shoots" by targeting the GM Vein along strike. A total of 20 holes totaling 1,713 m have been drilled on the GM Vein and the remainder of the metreage has now been allocated to the Argus Zone, a broad zone of near-surface gold mineralization situated three kilometres west-northwest of the past-producing Croesus Gold Mine and immediately north of the Pipestone Fault. The objective of planned drilling is to follow up with 50 m step-out holes on the best intersection from the fall 2023 drilling (0.96 g/t Au over 27.6 m in drill hole MC23-140) and expand the Argus Zone beyond the current strike length of 525 m and 200 m thickness.

Given the encouraging results, the Program has been upsized by 10% to 3,300 m and will be completed by the end of April. To maximize sample sizes, all drilling in the GM Vein target was completed with HQ-sized core. Drilling in the Argus Zone will be completed with NQ-sized core as in previous drill programs. Assay results will be released on an ongoing basis pending review and meeting Company quality assurance and quality control protocols.

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 1). 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 from 2020-2023 has unified the patchwork of patented and unpatented mining claims surrounding the Croesus Gold Mine into one coherent package (Figure 2) and enhanced the project's exploration potential.

The Project covers 70 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. that contains an Indicated Resource of 3.38 Moz at 0.93 g/t Au and an Inferred Resource of 157 koz at 0.85 g/t Au, and the Tower Gold Project being developed by Moneta Gold Inc. that contains an open pit Indicated Resource of 4.46 Moz at 0.92 g/t Au and an Inferred Resource of 8.29 Moz at 1.09 g/t Au1.

About the Timmins Area Gold Properties

Onyx owns 100% of each of its three Timmins properties. The Munro-Croesus Gold Project is located approximately 75 kilometres (47 miles) east of Timmins, proximal to the Porcupine-Destor and Pipestone Faults, and approximately two kilometres (1.2 miles) northwest and along trend of Mayfair Gold Corp.'s multi-million-ounce Fenn-Gib gold deposit. Mining occurred intermittently at Munro-Croesus between 1915 and 1936. The Golden Mile 140 square kilometre (54 square miles) property is located nine kilometres (5.6 miles) northeast of Newmont's multi-million-ounce Hoyle Pond deposit in Timmins. The Timmins South (Golden Perimetre) 187 square kilometres (72 square miles) property is located to the south and southeast of Timmins and surrounds the Shaw dome structure.

About Onyx Gold

Onyx Gold is an exploration company focused on well-established Canadian mining jurisdictions, with assets in Timmins, Ontario, and Yukon Territory. The Company's extensive portfolio of quality gold projects in the greater Timmins gold camp includes the Munro-Croesus Gold property, renowned for its high-grade mineralization, plus two additional earlier-stage large exploration properties, Golden Mile and Timmins South. Onyx Gold also controls four properties in the Selwyn Basin area of Yukon Territory, which is currently gaining significance due to recent discoveries in the area. Onyx Gold's experienced board and senior management team are committed to creating shareholder value through the discovery process, careful allocation of capital, and environmentally/socially responsible mineral exploration.

Additional Notes:

Starting azimuth, dip and final length (Azimuth/-Dip/Length) for the 14 drill holes reported today are noted as follows: MC24-149 (320/63/63), MC24-150 (320/74/81), MC24-151 (320/83/81), MC24-152 (320/66/78), MC24-153 (320/56/75), MC24-154 (320/74/84), MC24-155 (320/82/84), MC24-156 (320/69/81), MC24-157 (320/60/75/0, MC24-158 (320/51/75), MC24-159 (320/45/135), MC24-160 (320/80/84), MC24-161 (313.5/45/165), and MC24-162 (320/75/78).

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-metre interval to a maximum 1.5-metre interval, with an average 0.5 to 1.0-metre sample length.

Drill samples from the mineralized zones from each drill hole were delivered by truck in sealed woven plastic bags to MSA Labs laboratory facility in Timmins, Ontario for sample preparation followed by the photon assay method. MSA Labs operate meeting all requirements of International Standards ISO/IEC 17025:2017 and ISO 9001:2015.

Drill core samples are crushed to 70% passing 2mm, then a representative split is taken and pulverized to 85% passing 75mum. Gold is determined by photon assay of a 500-gram sample providing a true bulk reading. The Chrysos PhotonAssay method utilizes high energy x-rays causing excitation of atomic nuclei allowing enhanced analysis for gold.

Coarse rejects from MSA Labs and remaining drill core samples for each hole were then 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. ALS Geochemistry operate meeting all requirements of International Standards ISO/IEC 17025:2017 and ISO 9001:2015.

Gold is determined by fire-assay fusion of a 50-gram sub-sample with atomic absorption spectroscopy (AAS). Samples that return values >10 ppm gold from fire assay and AAS are determined by using fire assay and a gravimetric finish. Various metals including silver, gold, copper, lead and zinc are analyzed by inductively coupled plasma (ICP) atomic emission spectroscopy, following multi-acid digestion. The elements copper, lead and zinc are determined by ore grade assay for samples that return values >10,000 ppm by ICP analysis. Silver is determined by ore-grade assay for samples that return >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., Senior VP Exploration for HighGold Mining Inc. and a qualified person ("QP") as defined by Canadian National Instrument 43-101, has reviewed and approved the technical information contained in this release.

We seek Safe Harbor.