Grande Portage Resources Reports Positive Results from Preliminary Strength Testing of Mine Backfill Materials

All Samples Met or Exceeded Strength Criteria for Primary Mining Method

VANCOUVER, BC / ACCESS Newswire / July 6, 2026 / Grande Portage Resources Ltd. (TSXV:GPG)(OTCQX:GPTRF)(FSE:GPB) (“Grande Portage” or the “Company”) is pleased to provide a project update for the New Amalga Gold property near Juneau, Alaska.

The company has received laboratory results for preliminary backfill strength testing of CRF (cemented rockfill) samples which were cast using material sourced from core samples drilled during previous field seasons. The waste rock lithologies in these samples were selected to be aligned with those that will be encountered during mine development as well as those which would be present in ore sorter reject material.

These samples were cast into test cylinders using a 4% cement binder content (see pictures below) and were tested for uniaxial compressive strength (UCS) after 10-day and 17-day cure times.

All samples met or exceeded the preliminary strength criteria selected for overhand longhole stoping, the primary mining method planned for New Amalga. Based on these results, the company intends to advance both the waste rock from mine development as well as the ore sorter reject rock as feedstocks for making CRF backfill.

Future testwork with greater cement proportions will be undertaken to evaluate backfill for underhand stoping, a secondary mining method which is planned to be utilized for a small proportion of New Amalga production and which requires higher-strength backfill.

Ian Klassen, President and CEO comments: “This is an important de-risking milestone. We are very pleased with results of this initial testwork, demonstrating that development waste rock and ore sorter reject rock are appropriate feedstocks to advance for structural backfill use at New Amalga. This further validates our small-footprint strategy which results in all waste and reject rock being placed back underground, avoiding the need for permanent disposal facilities on surface. This approach can be expected to not only reduce surface disturbance but also lower future reclamation obligations and simplify environmental permitting.”

Additionally, geochemical testwork is currently in-progress on New Amalga core samples representing all major rock types present at the deposit to determine whether any have the potential to be reactive (acid-generating or metals leaching) over the long term. Previous limited testwork conducted in 2020-2021 on a small number of New Amalga wallrock samples showed favorable preliminary results, demonstrating significant net-acid-neutralizing potential ratios. For more details, see the company’s April 28, 2026 news release “Grande Portage Resources Initiates Full Scale Geochemical Characterization Program and Backfill Testwork for the New Amalga Gold Project”.

Table 1: Results of Preliminary Uniaxial Compressive Strength (UCS) Testing

*Preliminary UCS target was 0.46MPa accounting for scale factor for a 21cm x 9cm test cylinder and a 1.5x factor of safety

Fig. 1: Example of CRF Cylinder Cast for UCS Testing

Fig. 2: Example of CRF Cylinder Cast for UCS Testing

Project Summary:

The New Amalga Gold Project is located only 25km from Alaska’s capital city of Juneau and 6km from paved highway. The resource remains open to expansion in multiple directions and hosts an Indicated Resource of 1,438,500 ounces of gold at an average grade of 9.47 g/t Au (4,726,000 tonnes) and an Inferred Resource of 515,700 ounces of gold at an average grade of 8.85 g/t Au (1,813,000 tonnes).

The current development concept, as described in the Preliminary Economic Assessment (PEA) study with an effective date of February 11, 2026, envisions a small-footprint underground mining operation which would transport material offsite for processing by a third party, eliminating the need for an onsite gold recovery plant or tailings storage facility.

This setup is designed to provide several benefits:

• Eliminates the need to build a gold recovery plant, minimizing mine footprint, power requirements and reducing project construction CAPEX.

• Eliminates the need to develop a tailings disposal facility at the site, as no tailings would be generated.

• Removes the need for permanent waste rock storage facilities. Waste rock generated from mine development would be returned to the underground workings as stope backfill.

• No use of chemical reagents for gold processing at the site.

• Dramatically reduces land usage and overall environmental footprint.

• Greatly facilitates post-mining closure and reclamation.

• Simplifies the environmental review and permitting process.

Project Highlights:

• A 100% interest in the New Amalga Gold Project, located near infrastructure only 25km north of Juneau, Alaska and 6km from paved all-season highway (Fig. 4)

• Excellent economics demonstrated by NI43-101 Preliminary Economic Assessment (with an effective date of February 11, 2026):

  • At Base Case of US$3,200/oz gold price: after-tax NPV₅ of US$721m, after-tax IRR of 56%

  • At upside case of US$5,000/oz gold price: after-tax NPV₅ of US$1,557m, after-tax IRR of 91%

• The property is host to at least 8 large, long, gold bearing mesothermal veins

• 240 drill holes from 55 platforms totaling ~65,000 m confirm a large gold-quartz system

• Past drilling produced multi-ounce assays on several veins. Select samples include:

Deep Trench Vein: 15.3m grading 37.1 g/t Au, 8.3m grading 58.6 g/t Au, 11.6m grading 28.3 g/t Au
Goat Vein: 2.1m grading 74.2 g/t Au, 6.3m grading 15.7 g/t Au

Main Vein: 3.1m grading 79.2 g/t Au, 2.1m grading 37.2 g/t Au, 3.1m grading 13.9 g/t Au

Ridge Vein: 1.5m grading 43.0 g/t Au, 1.5m grading 29.2 g/t Au
Sleeping Giant Vein: 2.1m grading 15.4 g/t Au, 3.2m grading 20.7 g/t Au

See Fig. 3 below for approximate locations of selected intercepts.

• The Company’s updated NI43-101 Mineral Resource Estimate (MRE) with an effective date of July 17, 2024 reported an Indicated Resource of 1,438,500 ounces of gold at an average grade of 9.47 g/t Au (4,726,000 tonnes); and an Inferred Resource of 515,700 ounces of gold at an average grade of 8.85 g/t Au (1,813,000 tonnes), as well as an Indicated Resource of 891,600 ounces of silver at an average grade of 5.86 g/t Ag (4,726,000 tonnes); and an Inferred Resource of 390,600 ounces of silver at an average grade of 7.33 g/t silver (1,813,000 tonnes).

• The deposit is open to the north, south and at depth.

• Goat vein surface outcrop channel samples assayed 129.02 g/t gold (3.76 opt) and 290 g/t gold (8.46 opt) with 224 g/t silver (6.53 opt)

• LiDAR survey of property discovered numerous targets – the first of these tested confirmed gold discovery

• Received excellent metallurgical recoveries up to 98.2%

• Completed 6+ years of environmental baseline water sampling

• Current development strategy envisions a small-footprint underground mining operation with third-party offsite processing, eliminating the need for an onsite mill or tailings storage facility. This configuration reduces capital costs, greatly minimizes the project’s environmental footprint, and facilitates permitting.

• LOI signed with Goldbelt Inc (an Alaska Native Corporationorganized under the Alaska Native Claims Settlement Act) for development of an ore export terminal at Cascade Point, Goldbelt’s privately held parcel located only 22km from the project site.

Fig. 3: Approximate Locations of Selected Intercepts

Fig. 4: Location of the New Amalga Gold Project

Kyle Mehalek, P.E.., is the QP within the meaning of NI 43-101 and has reviewed and approved the technical disclosure in this release. Mr. Mehalek is independent of Grande Portage within the meaning of NI 43-101.

About Grande Portage:

Grande Portage Resources Ltd. is a publicly traded mineral exploration company focused on advancing the New Amalga Mine project, the outgrowth of the Herbert Gold discovery situated approximately 25 km north of Juneau, Alaska. The Company holds a 100% interest in the New Amalga property. The New Amalga gold system is open to length and depth and is host to at least six main composite vein-fault structures that contain ribbon structure quartz-sulfide veins. The project lies prominently within the 160km long Juneau Gold Belt, which has produced over eight million ounces of gold.

The Company’s updated NI#43-101 Mineral Resource Estimate (MRE) reported at a base case mineral resources cut-off grade of 2.5 grams per tonne gold (g/t Au) and consists of: an Indicated Resource of 1,438,500 ounces of gold at an average grade of 9.47 g/t Au (4,726,000 tonnes); and an Inferred Resource of 515,700 ounces of gold at an average grade of 8.85 g/t Au (1,813,000 tonnes), as well as an Indicated Resource of 891,600 ounces of silver at an average grade of 5.86 g/t Ag (4,726,000 tonnes); and an Inferred Resource of 390,600 ounces of silver at an average grade of 7.33 g/t silver (1,813,000 tonnes). The MRE was prepared by Dr. David R. Webb, Ph.D., P.Geol., P.Eng. (DRW Geological Consultants Ltd.) with an effective date of July 17, 2024. Additional information on the New Amalga Mine project is available in the technical report titled “Preliminary Economic Assessment for the New Amalga Gold Project Juneau District, Southeast Alaska” dated February 11, 2026, which is available under Grande Portage’s SEDAR+ profile at www.sedarplus.ca.

ON BEHALF OF THE BOARD

“Ian Klassen”
Ian M. Klassen
President & Chief Executive Officer
Tel: (604) 899-0106
Email: Ian@grandeportage.com

Cautionary Statement Regarding Forward-Looking Information

This news release includes certain “forward-looking statements” under applicable Canadian securities legislation. Forward-looking statements include estimates and statements that describe the Company’s future plans, objectives or goals, including words to the effect that the Company or management expects a stated condition or result to occur. Forward-looking statements may be identified by such terms as “believes”, “anticipates”, “expects”, “estimates”, “may”, “could”, “would”, “will”, or “plan”. Since forward-looking statements are based on assumptions and address future events and conditions, by their very nature they involve inherent risks and uncertainties as described in the Company’s filings with Canadian securities regulators. 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. The Company disclaims any intention or obligation to update or revise any forward-looking information, whether as a result of new information, future events or otherwise, other than as required by law.

Please note that under National Instrument 43-101, the Company is required to disclose that it has not based any production decision on NI 43-101-compliant reserve estimates, preliminary economic assessments, or feasibility studies, and historically production decisions made without such reports have increased uncertainty and higher technical and economic risks of failure. These risks include, among others, areas that are analyzed in more detail in a feasibility study or preliminary economic assessment, such as the application of economic analysis to mineral resources, more detailed metallurgical and other specialized studies in areas such as mining and recovery methods, market analysis, and environmental, social, and community impacts. Any decision to place the New Amalga Mine into operation at levels intended by management, expand a mine, make other production-related decisions, or otherwise carry out mining and processing operations would be largely based on internal non-public Company data, and on reports based on exploration and mining work by the Company and by geologists and engineers engaged by the Company.

NEITHER THE TSX VENTURE EXCHANGE NOR ITS REGULATION SERVICE PROVIDER (AS THAT TERM IS DEFINED UNDER THE POLICIES OF THE EXCHANGE) ACCEPTS RESPONSIBILITY FOR THE ADEQUACY OR ACCURACY OF THIS NEWS RELEASE

SOURCE: Grande Portage Resources Ltd.

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