Depth Extension Defined at Barry Deposit

Press Release

Val-d’Or, QC – June 4th, 2026 – Bonterra Resources Inc. (TSX-V: BTR, OTCQX: BONXF, FSE: 9BR2) (“Bonterra” or the “Company”) is pleased to announce the expansion of the Barry deposit at depth, as a result of deep drilling conducted at the Barry property (the “Project”). The Project is under a definitive earn-in and joint venture agreement (the “JV Agreement”) with Gold Fields Limited (“Gold Fields”). Under the JV Agreement, Gold Fields has the right to acquire a 70% interest in the Project by spending C$30 million in work expenditures, with a minimum spending commitment of C$10 million per year over a three-year period (see press release dated November 28, 2023, for more details).

Cesar Gonzalez, Executive Chairman and Interim CEO commented: “The discovery of mineralization extending at depth at the Barry deposit is a significant development, underscoring the potential to substantially increase gold ounces beyond the current mineral resources. The results released today were drilled approximately 100 meters from the boundary of the mineral resource estimate published last February. Notably, all five drill holes intersected potential mineralization consistent with Zone H at the Barry deposit. We congratulate our partner, Gold Fields, on this discovery and look forward to the continued advancement of exploration work on the Barry property.”

Highlights Barry Deep Drill Results

• 7.59 g/t Au over 1.9 m, including 17.75 g/t Au over 0.6 m, in hole BAR-26-0617
• 4.60 g/t Au over 2.5 m, including 11.1 g/t Au over 0.5 m, in hole BAR-26-0617
• 4.15 g/t Au over 0.4 m in hole BAR-26-0615
• 2.63 g/t Au over 1.6 m, including 7.52 g/t over 0.4 m, in hole BAR-26-0615
• 3.42 g/t Au over 2.1 m, including 5.77 g/t Au over 0.8 m, in hole BAR-26-0616
• 5.75 g/t Au over 1.2 m, including 13.4 g/t Au over 0.4 m, in hole BAR-26-0616
• 4.68 g/t Au over 0.4 m in hole BAR-26-0619
• 6.48 g/t Au over 2.2 m including 17.15 g/t Au over 0.5 m in hole BAR-26-0619

2026 Exploration Program Updates

The 2026 exploration program was designed to test targets located south-west and east of the Barry deposit and included deep drilling to evaluate the down-plunge extension of mineralization at depths of approximately 750 to 850 meters, as well as the eastern down-plunge extension of the deposit. Diamond drilling at Barry began in January with two drill rigs and was completed in April. A total of 14 diamond drill holes totaling 8,346 m has been completed. A total of 9,465 NQ core samples has been submitted to accredited laboratories, with about 30% of assay results pending.

The ground gravimetry survey that started last year is now complete. The survey was focused on improving a 200X200 m grid south of the Windfall Project and completing a 100X100 m survey around the Gladiator deposit.

Figure 1: Surface Plan View with 2026 Completed Drill Holes at Barry

Figure 2: Long Section View with Barry Deep Holes Drill Results

Barry Project Highlights

The Barry deposit is characterized by three dominant sets of structures, all dipping to the southeast.  The sub-vertical shear zones and the H-Series shear zones dipping 25 to 40 degrees are hosted within intermediate to mafic volcanics and tuffs with local felsic intrusions. Contact zones dip at 50 to 65 degrees along the lower and upper contacts of the D1, D2 and D3 felsic intrusions with mafic volcanics. Gold mineralization is associated with disseminated sulfides within shear zones and veins with local visible gold. The Barry deposit has been delineated over 1.4 kilometers along strike and 700 m vertically and remains open for further expansion.

The latest Mineral Resource Estimate (the “2026 MRE”, press release dated February 23, 2026) contains an Open pit mineral resources 7.8 million tonnes (“Mt”) at an average grade of 1.67 g/t Au for 417 thousand ounces (“Koz”) of Measured & Indicated Mineral Resources, plus 125 thousand tonnes (“Kt”) at 2.32 g/t Au for 9 Koz of Inferred Mineral Resources. Underground Mineral Resources contains 4.1 Mt at an average grade of 3.47 g/t Au for 457 Koz of Measured & Indicated Mineral Resources, plus 8.8 Mt at 3.41 g/t Au for 972 Koz of Inferred Mineral Resources (see press release dated February 23, 2026).

The Barry Mine was in production between 2008 and 2010, during which time it produced approximately 44,000 ounces of gold. In 2018, Bonterra constructed an underground exploration ramp extending to 100 m below surface. The Company currently maintains a mining lease for 1.2 million tonnes, permitting extraction by both open pit and underground methods. The project is supported by established infrastructure and essential permits required to facilitate a restart of operations.

Table 1: Drill Hole Locations –Barry Deep Target

Hole ID	Easting	Northing	Elevation (m)	Azimuth (°)	Dip (°)	Length (m)
BAR-26-0615	444424	5425623	394	329	-60	1,002
BAR-26-0616	444417	5425373	392	330	-60	1,179
BAR-26-0617	444640	5425661	393	329	-59	1,143
BAR-26-0618	444186	5425344	393	331	-58	1,050
BAR-26-0619	444650	5425896	392	332	-60	999

UTM Coordinates, System: NAD83 Zone 18N

Table 2: Significant Mineralized Intersections from Drilling on the Barry Deep Target

Hole ID	Including	From (m)	To (m)	Length (m)	Grade (Au g/t)	Metal Factor (length x grade)
BAR-26-0615		771.1	771.5	0.40	4.15	1.66
		779.4	781	1.60	2.63	4.21
	Including	779.4	779.8	0.40	7.52	3.00
	Including	780.5	781	0.50	1.73	0.86
BAR-26-0616		937.8	939.0	1.20	5.75	6.90
	Including	937.8	938.6	0.80	1.93	1.04
	Including	938.6	939.0	0.40	13.40	5.36
		1,035.8	1,037.9	2.10	3.42	7.18
	Including	1,035.8	1,036.2	0.40	0.85	0.34
	Including	1,036.2	1,037.0	0.80	5.77	4.62
	Including	1,037.0	1,037.4	0.40	2.66	1.06
BAR-26-0617		796.6	798.5	1.90	7.59	14.42
	Including	796.6	797.2	0.60	4.46	2.68
		797.2	797.8	0.60	17.75	10.65
		797.8	798.5	0.70	1.10	0.77
		879.0	881.5	2.50	4.60	11.50
	Including	879.0	879.4	0.40	1.37	0.55
	Including	879.4	879.7	0.30	8.97	2.69
	Including	879.7	881.0	1.30	1.46	1.90
	Including	881.0	881.5	0.50	11.10	5.55
BAR-26-0618		878.3	879.0	0.70	0.97	0.68
BAR-26-0619		581.6	582.0	0.40	4.68	1.87
		888.0	890.2	2.20	6.48	14.26
	Including	888.0	888.4	0.40	3.29	1.32
	Including	888.4	888.8	0.40	5.29	2.12
	Including	888.8	889.1	0.30	3.86	1.16
	Including	889.1	889.4	0.30	3.49	1.05
	Including	889.4	889.7	0.30	0.14	0.04
	Including	889.7	890.2	0.50	17.15	8.58

1. True width determination is currently unknown but is estimated from 55 to 80% of the reported core length interval for the zone.
2. Assays are uncut except where indicated.
3. Intercepts have not been correlated to individual zones or vein domains at this time.

Quality Control and Reporting Protocols

NQ core assays were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at ALS Laboratories in Val-d’Or, Québec, or Vancouver, British Colombia. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. All samples are also analyzed for multi-elements, including silver, using Four Acid Digestion-ICP-MS method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control (“QA/QC”) and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes.

Qualified Person

M. Donald Trudel, P.Geo. (OGQ # 813), Director Geology for the Company, has reviewed and approved the technical information contained in this press release. Mr. Trudel is a qualified person as defined by National Instrument 43-101 on standards of disclosure for mineral projects.

About Bonterra Resources

Bonterra is a Canadian gold exploration company with a portfolio of advanced exploration assets anchored by a central milling facility in Québec, Canada. The Company’s assets include the Gladiator, Barry⁽¹⁾, Moroy, and Bachelor⁽²⁾ gold deposits, which collectively hold 16.8 million tonnes (“Mt”) at an average grade of 3.02 g/t Au for 1.63 million ounces (“Moz”) of Measured & Indicated Mineral Resources, plus 15.6 Mt at 4.32 g/t Au for 2.17 Moz at an average grade of 4.32 g/t Au of Inferred Mineral Resources.

In November 2023, the Company entered into an earn-in and joint venture agreement with Osisko Mining Inc. (“Osisko Mining”) for the Urban-Barry properties (the “JV Agreement”), which include the Gladiator and Barry deposits. In October 2024, Gold Fields Ltd, through a wholly owned Canadian subsidiary, completed the acquisition of Osisko Mining for C$2.16 billion. Gold Fields is now the counterparty to the JV Agreement and can continue to earn a 70% interest in the joint venture by incurring C$30 million in work expenditures on or before November 2026 (including expenditures incurred by Osisko Mining prior to October 2024). This strategic transaction highlights Bonterra’s dedication to advancing its exploration assets, marking a significant step towards development.

1. See news release of the Company dated February 23, 2026, and titled “Bonterra Reports Significant Mineral Resources Growth at Barry and Gladiator Deposits” for further details.
2. See news release of the Company dated April 1st, 2026, and titled “Bonterra Reports Significant Mineral Resource Growth at Bachelor and Moroy, 100% owned Deposits and Provides Corporate Updates” for further details.

This news release, including the drill results and the Mineral Resource Estimates referenced herein, has been prepared solely by the Company and is based on information available to the Company as of the date hereof. Neither Gold Fields Limited nor its affiliate Windfall Mining Group Inc. has verified, approved or endorsed the Mineral Resource Estimates or the content of this news release, and no representation or warranty is made by Gold Fields Limited or Windfall Mining Group Inc. with respect thereto. References to the Phoenix Joint Venture are provided for contextual purposes only and should not be construed as statements made by, or on behalf of, Gold Fields Limited or Windfall Mining Group Inc.

FOR ADDITIONAL INFORMATION

Cesar Gonzalez, Executive Chairman & Interim CEO
ir@btrgold.com

2872 Sullivan Road, Suite 2, Val d’Or, Québec J9P 0B9

819-825-8678 | Website: www.btrgold.com

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