Borealis Advances Sandman Toward Development with 5,000 Metre Drill Program

• Program designed to advance Sandman toward development through metallurgical and geotechnical testing
• Initial drilling to support engineering studies, mine planning and permitting activities
• Follow-up drilling to target resource expansion and district-scale exploration opportunities
• Metallurgical and geotechnical test work planned across all four Sandman deposits

Vancouver, British Columbia--(Newsfile Corp. - June 10, 2026) - Borealis Mining Company Limited (TSXV: BOGO) (OTCQB: BORMF) (FSE: L4B0) ("Borealis" or the "Company") is pleased to announce the commencement of a 5,000 metre drilling program at its wholly-owned Sandman Gold Project ("Sandman" or the "Project") in Humboldt County, Nevada. Drilling is expected to begin on or about June 19^th, 2026 and continue for several months.

The program represents the next phase in advancing Sandman toward development and is designed to generate the technical information required to support future engineering studies, mine planning, and permitting activities while continuing to evaluate opportunities to expand the project's resource base.

Approximately 1,660 metres of the program will be dedicated to metallurgical and geotechnical drilling across the Silica Ridge, North Hill, Abel Knoll, and Southeast Pediment deposits, with the balance of the program focused on resource expansion and exploration drilling. The initial phase is intended to generate critical engineering, mine planning, and permitting data, while the second phase will evaluate opportunities to expand existing resources and test new exploration targets throughout the district.

Figure 1: Sandman Property and Mineral Resource Outlines

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Sandman is an advanced-stage gold project located approximately 25 kilometres northwest of Winnemucca, Nevada. The project hosts a pit-constrained mineral resource containing 433,000 ounces of gold in the Indicated category grading 0.73 g/t gold and 60,800 ounces of gold in the Inferred category grading 0.58 g/t gold. The resource includes approximately 300,600 ounces of oxide gold, representing a significant portion of the project's potential heap-leach feed, and is distributed across four principal deposits: Silica Ridge, North Hill, Abel Knoll, and Southeast Pediment. A Preliminary Economic Assessment ("PEA") completed earlier this year demonstrated robust economics, including an after-tax NPV(6%) of approximately US$203 million and an IRR of approximately 105% at a gold price of US$2,600 per ounce. The PEA outlines a conventional open-pit, heap-leach operation producing approximately 38,000 ounces of gold annually over a nine-year mine life.

Table 1: Sandman Mineral Resource Estimate (2021)

The initial phase of drilling will focus on metallurgical and geotechnical testing across each of the four deposits. Metallurgical drilling will provide representative samples for recovery testing and future process optimization studies, while geotechnical drilling will collect information required for pit slope design, mine planning, infrastructure layout, and permitting activities.

The Company believes this work will provide a critical technical foundation for evaluating future development scenarios at Sandman and advancing the project through key engineering and permitting milestones. The data generated from the program is expected to support future technical studies while helping define a potential pathway toward production.

Following completion of the metallurgical and geotechnical program, Borealis plans to allocate the remaining metres toward resource expansion and exploration drilling. The program will test extensions of known mineralization adjacent to existing deposits and evaluate several high-priority exploration targets identified through compilation of historical exploration data and recent geological interpretation.

Management Commentary

"With production activities progressing well at the Borealis Mine, we are now focused on advancing the next phase of growth within our Nevada portfolio. Sandman already hosts nearly 500,000 ounces of gold, robust economics from our recently completed PEA, and substantial exploration upside. This program is designed to generate the technical information required to advance the project toward future development while continuing to evaluate opportunities to expand the resource base and unlock additional value across the district. We believe the combination of an established resource, a significant oxide component, strong infrastructure, and exploration upside positions Sandman as a compelling future growth asset within our Nevada portfolio."

The Company will provide additional updates as drilling progresses and analytical results become available.

Atrium Research Engagement

The Company also announces that it has entered into an agreement dated June 9, 2026, with an effective date of June 1, 2026, to engage the services of Atrium Research Corporation ("Atrium"), a leading company sponsored research firm. Atrium will publish various research reports on Borealis based on publicly available information, industry data, and discussions with management. Atrium will also host two recorded interviews with Borealis's management team to present the investment case in an interview format. In exchange for its research services, Atrium will receive cash compensation in the amount of $12,000 per quarter for the services listed above. The services will be provided for 12 months. At the end of the 12 month term, the agreement will be deemed to remain in place and be extended on a quarter-to-quarter basis at $12,000 per quarter, unless otherwise agreed to by the parties or the agreement is terminated by either party. This engagement is subject to the approval of the TSX Venture Exchange.

Atrium and the Company are arm's-length parties, and neither Atrium nor its insiders holds any shares or options to purchase shares in the issued and outstanding capital of the Company.

About Atrium Research

Atrium Research provides institutional quality company sponsored research on public equities in North America. Its investment philosophy takes a 3-5 year view on equities currently being overlooked by the market. Its research process emphasizes understanding the key performance metrics for each specific company, trustworthy management teams, and an in-depth valuation analysis. Atrium Research is wholly owned and operated by its Co-Founders, Ben Pirie and Nicholas Cortellucci.

About the Sandman Gold Project

Sandman is a conventional open-pit, heap-leach gold project located in Humboldt County, Nevada, approximately 12 miles northwest of Winnemucca. The Project hosts four known deposits—North Hill, Silica Ridge, Southeast Pediment, and Abel Knoll—and benefits from proximity to infrastructure and Borealis' existing operations.

A 2026 PEA demonstrates robust project economics for a conventional, low-strip, heap-leach development scenario. At a base case gold price of US$2,600 per ounce, the Project generates an estimated after-tax net present value (6% discount rate) of approximately US$203 million and an internal rate of return of approximately 105%, with average annual production of approximately 38,000 ounces of gold over an approximately nine-year mine life. Life-of-mine gold production is estimated at approximately 340,000 ounces, with all-in sustaining costs of approximately US$1,823 per ounce and initial capital of approximately US$36 million.

The PEA also highlights strong leverage to gold prices, with materially higher returns at prices above the base case.

The Project is designed as a phased, capital-efficient development with the potential to utilize Borealis' existing adsorption–desorption–recovery ("ADR") facility, providing a credible pathway toward reduced capital intensity and accelerated development.

Qualified Person and Cautionary Statement