Mr. Brock Colterjohn reports

ONYX GOLD REPORTS NEW HIGH-GRADE VEIN DISCOVERY AT MUNRO-CROESUS PROJECT, TIMMINS, ONTARIO

Onyx Gold Corp. has released initial exploration results from its 2023 fall drill program in the Timmins gold camp, Ontario. The first assay results have been returned for drill hole MC23-132, which tested a prospective area 350 metres (1,148 feet) northwest of the former Croesus gold mine. The Croesus gold mine is famous for yielding some of the highest-grade gold mined in Ontario.

The completed program included about 4,000 metres (m) of diamond drilling with one drill rig and focused on targets proximal to the historic high-grade Croesus gold mine, and on the new bulk-tonnage-style Argus zone discovered in 2022.

Highlight assay results for drill hole MC23-132 include:

• 121.8 grams per tonne (g/t) (3.55 ounces per ton (opt)) gold (Au) over 0.9 m (true width); including

• 363.0 g/t (10.59 opt) Au over 0.3 m (true width).

The drill hole intersected a 30-centimetre-wide quartz vein containing abundant visible gold that returned 363 g/t (10.59 opt) Au over 0.3 m, representing 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 (3.55 opt) Au over 0.9 m and was intersected approximately 60 m vertically below surface. This new vein discovery represents an entirely new high-grade quartz vein in a geological setting comparable to the mined-out, bonanza-grade Croesus vein.

"The intersection of multiounce gold grades within a completely new vein system parallel to the renowned Croesus vein is a direct validation of the team's recent advancements in geological and structural modelling in the area," said Brock Colterjohn, president and chief executive officer. "The historic Croesus gold mine produced some of the highest-grade gold ever mined in Ontario, with an average head grade of 95.3 g/t (2.78 opt) gold. This new vein underscores the opportunity for additional discoveries within an established high-grade gold environment. It is an excellent start to Onyx Gold's inaugural drill program in Ontario."

"The Timmins camp is one of the most prolific gold-producing regions in the world with multiple operating mines and excess milling capacity. Onyx Gold has established one of the largest land positions in the camp not owned by a producer. Much of this land package is in prime high-potential geology with little or no work completed for decades. Our land tenure represents particularly attractive opportunities for discoveries such as this. This new vein remains open in all directions, and we look forward to further expanding this high-grade discovery in a winter drill campaign. We are also looking forward to results from the rest of our fall program which will be reported in due course."

Discussion of results

A total of five holes (MC23-130 to MC23-134) totalling 872 m were completed by the company in late October/early November to follow up north and south of drill hole MC22-92 drilled by the previous operator, HighGold Mining Inc., which intersected a narrow quartz vein that returned 14.0 g/t Au over 0.6 metre in a broader interval grading 3.4 g/t Au over 2.6 m (see HighGold Mining Inc. press release from March 30, 2022). The area was targeted for its similar geological setting to the Croesus gold mine -- specifically, the occurrence of a parallel vein to the Croesus vein within a particular basalt flow unit that is locally brecciated and enriched in sulphides (the Croesus flow). The Croesus flow is interpreted to play an important role in the deposition of exceptionally high concentrations of gold within the Croesus vein.

Results have been returned from hole MC23-132, a 25-metre stepout south of MC23-92, which intersected what is believed to be a new vein in a parallel orientation to the Croesus vein within the upper portion of the Croesus flow. The quartz vein was intersected from 83.0 to 83.3 metres downhole within sulphidic pillowed Croesus flow and returned the highest-grade interval on the property to date of 363.0 g/t Au over 0.3 m (true width) within a broader structural zone averaging 121.8 g/t Au over 0.9 m (true width). The quartz vein is characterized by massive, white-grey quartz with abundant fine-grained aggregates of visible gold throughout and in and along the margins of pyrite grains. The quartz contains coarse, disseminated and fracture-filling pyrite and trace, fine-grained sphalerite, and arsenopyrite. The 363.0 g/t Au assay was obtained by gold gravimetric analysis (Au-GRA22) at the ALS Canada lab in North Vancouver. A gold screen analysis (Au-SCR21) was also performed and returned a total gold value of 342.0 g/t Au.

Between 1915 and 1936, the Croesus mine produced 14,854 ounces of gold mined from 5,333 tons with an average grade of 2.78 opt Au (95.3 g/t Au) as reported by the Ontario Department of Mines in 1951. Note -- this production number did not include the ore that was mined and shipped in packing crates directly to the Royal Canadian Mint. Five gold samples purchased by the Ontario Bureau of Mines for exhibition purposes and now in possession of the Royal Ontario Museum in Toronto, Ont., weigh 85 pounds collectively and contain 480.7 ounces of gold or 11,310 oz gold per ton (387,727 g/tonne). The Croesus vein and the new vein are parallel northeast-striking, east-southeast-dipping shear veins that contain abundant visible gold where they intersect the permissive host lithology (Croesus flow). This highlights the opportunity to discover additional parallel high-grade veins within the Croesus flow.

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. This large, 100-per-cent-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 and enhanced the exploration potential of the project.

The project covers 70 square kilometres (27 square miles) 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 million ounces at 0.93 g/t Au and an inferred resource of 157 thousand ounces at 0.85 g/t Au, and the Tower gold project being developed by Moneta Gold Inc. which 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 Au.

Fourth quarter 2023 Ontario drill program

The company successfully completed its planned fall drill program on Dec. 2 with 4,078 metres drilled in 19 holes. Approximately half of the drilling budget was focused on expansion drilling at the Argus zone located on the western side of the property, with the remaining half of the drilling budget focused on follow-up holes at targets proximal to the historic high-grade Croesus gold mine. Assay results from the fall program are currently pending and will be released in due course.

About the Timmins area gold properties

Onyx owns 100 per cent 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 multimillion-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 multimillion-ounce Hoyle Pond deposit in Timmins. The Timmins South (Golden Perimeter) 187-square-kilometre (72 square miles) property is located to the south and southeast of Timmins and surrounds the Shaw dome structure.

About Onyx Gold Corp.

Onyx Gold is an exploration company focused on well-established Canadian mining jurisdictions, with assets in Timmins, Ont., and the 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 the 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.

Qualified person and quality assurance

Ian Cunningham-Dunlop, PEng, executive vice-president for Onyx Gold and a qualified person (QP) as defined by Canadian National Instrument 43-101, has reviewed and approved the technical information contained in this release.

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