Alamos Gold Announces Island Gold District Base Case Life of Mine Plan Outlining One of the Largest and Lowest-Cost Gold Mines in Canada with Significant Upside

2025-06-23

TSX - Toronto Stock Exchange · Gold · Canada

All amounts are in United States dollars, unless otherwise stated.

TORONTO, June 23, 2025 (GLOBE NEWSWIRE) -- Alamos Gold Inc. ( TSX:AGI; NYSE:AGI ) (“Alamos” or the “Company”) today reported results of the Base Case Life of Mine Plan (“Base Case LOM Plan”) completed on the Island Gold District operation, located in Ontario, Canada. The Base Case LOM Plan integrates Island Gold and Magino as one consolidated long-life operation that is expected to become one of the largest, lowest-cost, and most profitable gold mines in Canada. An Expansion Study is expected to be released in the fourth quarter of 2025 detailing the significant upside potential within the Island Gold District beyond the Base Case LOM Plan.

The Base Case LOM Plan has been updated to reflect the current costing environment, significant growth in Mineral Reserves at Island Gold, operating savings resulting from the use of a larger and more efficient Magino mill, and scope changes since the Phase 3+ Expansion Study (“Phase 3+ Study”), which was completed in 2022. The Base Case LOM Plan includes Mineral Reserves only at Island Gold and Magino. Both deposits have significant Measured, Indicated and Inferred Mineral Resources, which have not been factored into the Base Case LOM Plan and economic analysis. All amounts are in United States dollars, unless otherwise stated.

“The Base Case Plan for the Island Gold District outlines an attractive, long-life operation that is expected to become one of Canada’s largest, lowest-cost, and most profitable gold mines. This is a first look at an operation with significant upside potential which we expect to detail in an Expansion Study later this year. We expect this to include a larger Mineral Reserve through ongoing Mineral Resource conversion, and a potential further expansion up to 20,000 tonnes per day, supporting an even larger, more valuable, and profitable operation. Longer-term, we see excellent opportunities for that value to continue to grow through ongoing exploration success at Island Gold, and a number of emerging higher-grade regional targets that have the potential to support multiple sources of ore within an expanded mill,” said John A. McCluskey, President and Chief Executive Officer.

Base Case LOM Plan Highlights:

Average annual gold production of 411,000 ounces starting in 2026 and over the initial 12 years, a 43% increase from the mid-point of 2025 production guidance driven by the completion of the Phase 3+ Expansion

Average annual production of 306,000 ounces over the 20-year Mineral Reserve life Significant upside potential through a further expansion of the operation, and the expected conversion of a significant portion of the large Mineral Resource base to Mineral Reserves through ongoing delineation drilling

Low-cost structure: average mine-site all-in sustaining costs (“mine-site AISC”) of $915 per ounce over the initial 12 years (2026+), a 19% decrease from the mid-point of 2025 guidance

Average total cash costs of $581 per ounce over the initial 12 years (average $699 per ounce over the life of mine) Average AISC of $1,003 per ounce over the life of mine, an 11% decrease from 2025 guidance

Long-life operation supported by a large and growing Mineral Reserve base

48% increase in total Mineral Reserves to 6.3 million ounces (88.6 million tonnes (“mt”) grading 2.23 grams per tonne (“g/t Au”), including: 4.1 million ounces grading 10.85 g/t Au (11.8 mt) at Island Gold underground, up 80% from the end of 2024 reflecting the conversion of Mineral Resources 2.2 million ounces grading 0.91 g/t Au (76.9 mt) at Magino open pit, up 12% from the end of 2024

Significant upside potential expected to be outlined in an Expansion Study in the fourth quarter of 2025

Base Case LOM Plan based only on Mineral Reserves and long-term milling rates of 12,400 tonnes per day (“tpd”) Expansion Study expected to include an increase in milling rates potentially to between 18,000 and 20,000 tpd supporting higher throughput rates from both Island Gold and Magino, and

The incorporation of a larger Mineral Reserve through the expected conversion of a significant portion of existing Mineral Resources, which consist of: Island Gold Underground M&I Mineral Resources: 1.0M oz grading 10.49 g/t Au (3.1 mt) Inferred Mineral Resources: 1.3M oz grading 16.88 g/t Au (2.4 mt)

Magino Open Pit M&I Mineral Resources: 1.8M oz grading 0.91 g/t Au (60.3 mt) Inferred Mineral Resources: 1.2M oz grading 0.92 g/t Au (40.3 mt)

Low capital intensity

Growth capital of $453 million with the majority to be spent over the next two years, focused on completing the Phase 3+ Expansion and Magino mill expansion to 12,400 tpd Sustaining capital of $1,808 million over the life of mine, or $304 per ounce Sustaining capital intensity expected to decrease within Expansion Study reflecting a larger Mineral Reserve leveraging existing infrastructure Total all-in cost of $1,079 per ounce, including total capital intensity of $380 per ounce

Attractive base case economics with significant upside

After-tax net present value (“NPV”) (5%) of $4.5 billion, (base case long-term gold price assumption of $2,400 per ounce and USD/CAD foreign exchange rate of $0.75:1) After-tax NPV (5%) of $6.7 billion, at current gold prices of approximately $3,300 per ounce Expansion Study is expected to demonstrate attractive economics with a further increase in value reflecting a larger Mineral Reserve and higher throughput rates

Phase 3+ Expansion expected to be completed during the second half of 2026

Base Case LOM Plan is consistent with existing three-year production guidance The slight delay in the completion of the Phase 3+ Expansion (from the first half of 2026 previously) is not expected to impact production or cost guidance in 2026 and 2027 Work on the Phase 3+ Expansion has been largely de-risked with a number of key projects substantially complete including the shaft surface infrastructure, and shaft development which is currently at 92% of its ultimate planned depth

Low and decreasing Greenhouse Gas (“GHG”) emission intensity

29% reduction of GHG emissions per ounce from already low levels which are currently 57% below the industry average. This is expected to be achieved through the completion of the Phase 3+ Expansion, and connection of the Magino mill to grid power in 2026

Fully funded growth: ongoing free cash flow with significant growth expected in 2026

Island Gold District is expected to self finance all remaining growth capital at current gold prices with significant free cash flow growth following the completion of the Phase 3+ Expansion in 2026

| Base Case LOM Plan Highlights | | | Production | | | Mine life (years) | 20 | | Phase 3+ Expansion completion date | H2 2026 | | | | | Total gold production (000 ounces) | 6,112 | | Average annual gold production – 12-year average, 2026+ (000 ounces) | 411 | | Average annual gold production – life of mine (000 ounces) | 306 | | | | | Total mill feed (000 tonnes) | 88,648 | | Average mill throughput – 2027+ (tpd) | 12,400 | | Average gold grade (g/t Au) | 2.23 | | Average Island Gold ore throughput – 2027+ (tpd) | 2,400 | | Average Island Gold ore grade milled (g/t Au) | 10.85 | | Average Magino ore throughput (tpd) | 10,000 | | Average Magino ore grade milled (g/t Au) | 0.91 | | Average recovery (%) | 96.3% | | Operating Costs | | | Open pit mining cost (C$/tonne of total material mined) | $4.24 | | Underground mining cost (C$/tonne of ore mined) | $124 | | Processing cost (C$/tonne of ore milled) | $16.74 | | G&A cost (C$/tonne of ore milled) | $13.73 | | | | | Total cash cost – 12-year average, 2026+ (per ounce sold) 1,2 | $581 | | Total cash cost – life of mine (per ounce sold) 1,2 | $699 | | Mine-site all-in sustaining cost – 12-year average, 2026+ (per ounce sold) 1,2 | $915 | | Mine-site all-in sustaining cost – life of mine (per ounce sold) 1,2 | $1,003 | | Capital Costs (millions) | | | Growth capital expenditure | $453 | | Sustaining capital expenditure 5 | $1,808 | | Total capital expenditure – life of mine | $2,261 | | Total capital expenditure (per ounce sold) – life of mine 2 | $380 | | Total all-in cost (per ounce sold) – life of mine 2 , 3 | $1,079 | | Base Case Economic Analysis: $2,400 per ounce Gold Price (USD/CAD foreign exchange rate of $0.75:1) 4 | | | NPV @ 0% discount rate (millions, after-tax) | $6,417 | | NPV @ 5% discount rate (millions, after-tax) | $4,477 | | Economic Analysis at $3,300 per ounce Gold Price (USD/CAD foreign exchange rate of $0.75:1) | | | NPV @ 0% discount rate (millions, after-tax) | $9,682 | | NPV @ 5% discount rate (millions, after-tax) | $6,667 |

1. Total cash costs and mine-site all-in sustaining costs include royalties and silver as a by-product credit 2. Please refer to the Cautionary Notes on non-GAAP Measures and Additional GAAP Measures 3. Total all-in cost per ounce sold is calculated as total cash cost per ounce plus total capital per ounce sold over the life of mine 4. The Base Case LOM Plan includes a gold price of $3,000/oz in 2025 through to 2027, and a long-term (2028+) gold price of $2,400/oz, as well as a USD/CAD foreign exchange rate of $0.73:1 in 2025, $0.74:1 in 2026 and 2027, and $0.75:1 from 2028 onwards 5. Sustaining capital includes reclamation and capital leases

Prior Disclosure Regarding Island Gold Mine

As a result of a review by staff of the Ontario Securities Commission, the Company is providing the following corrective information regarding its disclosure with respect to the Island Gold Mine .

The 2025 Base Case Island Gold District Technical Report is being prepared and will be disclosed without the inclusion of Inferred Mineral Resources in economic analyses, including production schedules, mine life and cash flow models. The 2025 Base Case Island Gold District Technical Report will supersede any prior technical reports published by Alamos with respect to the Island Gold Mine.

Prior public disclosure regarding the Island Gold Mine included the use of Inferred Mineral Resources in economic analyses, including production schedules, mine life and cash flow models. Such disclosure was prohibited under paragraph 2.3(1)(b) of National Instrument 43-101 _Standards of Disclosure for Mineral Projects _( NI 43-101 ), which restricts public disclosure of the results of an economic analysis that includes or is based on Inferred Mineral Resources. In addition, NI 43-101 incorporates by reference the CIM Definition Standards (2014), which states that Inferred Mineral Resources must not be included in the economic analysis, production schedules, or estimated mine life in publicly disclosed prefeasibility or feasibility studies, or in the life of mine plans and cash flow models of developed mines. Inferred Mineral Resources are considered too speculative geologically to have economic considerations applied to them that would enable them to be categorized as Mineral Reserves and there can be no certainty that the results of an economic analysis including Inferred Mineral Resources would be realized.

Mineral Reserves and Resources

An updated Proven and Probable Mineral Reserve totaling 88.6 mt, grading 2.23 g/t Au, containing 6.3 million ounces of gold has been included in the Base Case LOM Plan. This represents a 48% increase from the 4.3 million ounces reported at the end of 2024, reflecting the conversion of Measured, Indicated and Inferred Mineral Resources at Island Gold and Magino. Only Mineral Reserves have been incorporated into the Base Case LOM plan and economic analysis.

Island Gold’s updated Mineral Reserve increased by 80% to 4.1 million ounces, driven by Mineral Resource conversion. An updated classification methodology has been adopted based on definition drilling, extensive historical and current production data, reconciliation, and underground mapping, which demonstrates that Indicated Mineral Resource continuity can be reliably established with an average drill spacing of 40 metres, versus 25 metres previously. This contributed to the conversion of a portion of the large Inferred Mineral Resource to Measured & Indicated Mineral Resources, which was subsequently converted to Mineral Reserves.

Mineral Reserves – Effective as of December 31, 2024

| Proven and Probable Gold Mineral Reserves | | | | | | | | | | | | June 2025 Update | February 2025 Update | % Change | | | | | | | | | Tonnes | Grade | Ounces | Tonnes | Grade | Ounces | Tonnes | Grade | Ounces | | | (000’s) | (g/t Au) | (000’s) | (000’s) | (g/t Au) | (000’s) | (000’s) | (g/t Au) | (000’s) | | Island Gold | | | | | | | | | | | Proven | 821 | 11.82 | 312 | 727 | 12.74 | 298 | 18% | -11% | 5% | | Probable | 10,947 | 10.78 | 3,795 | 5,505 | 11.23 | 1,987 | 112% | -10% | 91% | | Proven and Probable | 11,769 | 10.85 | 4,107 | 6,232 | 11.40 | 2,285 | 89% | -5% | 80% | | Magino | | | | | | | | | | | Proven | 22,163 | 0.88 | 626 | 19,684 | 0.89 | 561 | 13% | -1% | 12% | | Probable | 54,710 | 0.92 | 1,613 | 48,715 | 0.92 | 1,447 | 12% | 0% | 11% | | Proven and Probable | 76,873 | 0.91 | 2,240 | 68,400 | 0.91 | 2,008 | 12% | 0% | 12% | | Island Gold District | | | | | | | | | | | Proven | 22,984 | 1.27 | 938 | 20,411 | 1.31 | 859 | 13% | -4% | 9% | | Probable | 65,657 | 2.56 | 5,408 | 54,220 | 1.97 | 3,434 | 22% | 28% | 57% | | Proven and Probable | 88,642 | 2.23 | 6,347 | 74,632 | 1.79 | 4,293 | 19% | 25% | 48% |

Mineral Reserves reported are consistent with the CIM Definition Standards for Mineral Resources and Mineral Reserves Mineral Reserves are reported to a cut-off grade of 3.78 Au g/t at Island Gold and 0.30 Au g/t for Magino The cut-off grades are based on a gold price of $1,600/oz Au at both Island Gold and Magino Silver is not used in the cut-off grade calculation Totals may not add up due to rounding Chris Bostwick, FAusIMM, Senior Vice President, Technical Services is the Qualified Person for Magino’s Mineral Reserve estimate. Mr. Bostwick is a Qualified Person within the meaning of Canadian Securities Administrator's National Instrument 43-101 ("NI 43-101") Nathan Bourgeault, P.Eng., Manager, Technical Services for the Island Gold District is the Qualified Person for Island Gold’s Mineral Reserve estimate. Mr. Bourgeault is a Qualified Person within the meaning of Canadian Securities Administrator's National Instrument 43-101 ("NI 43-101")

Mineral Resources for Island Gold and Magino, as detailed below, have not been included in the Base Case LOM Plan and represent potential upside. A significant portion of Mineral Resources at Island Gold, and Measured and Indicated Mineral Resources at Magino, are expected to be converted to Reserves and incorporated into the Expansion Study to be released in the fourth quarter of 2025. The decrease in Inferred Mineral Resources at Island Gold reflects the conversion to Measured and Indicated Mineral Resources and Mineral Reserves.

The Mineral Resource conversion rate to Reserves at Island Gold continues to average more than 90%. This high rate of conversion is expected to continue based on ongoing success with the delineation drilling program.

Mineral Resources – Effective as of December 31, 2024

| Measured and Indicated Gold Mineral Resources (exclusive of Mineral Reserves) | | | | | | | | | | | | June 2025 Update | February 2025 Update | % Change | | | | | | | | | Tonnes | Grade | Ounces | Tonnes | Grade | Ounces | Tonnes | Grade | Ounces | | | (000’s) | (g/t Au) | (000’s) | (000’s) | (g/t Au) | (000’s) | (000’s) | (g/t Au) | (000’s) | | Island Gold | | | | | | | | | | | Measured | 470 | 14.66 | 222 | 235 | 10.96 | 83 | 100% | 34% | 167% | | Indicated | 2,640 | 9.75 | 827 | 1,898 | 8.49 | 518 | 39% | 15% | 60% | | Measured and Indicated | 3,110 | 10.49 | 1,049 | 2,113 | 8.76 | 601 | 47% | 20% | 75% | | Magino | | | | | | | | | | | Measured | 5,061 | 0.87 | 141 | 5,579 | 1.00 | 179 | -9% | -13% | -21% | | Indicated | 55,209 | 0.91 | 1,615 | 57,110 | 0.94 | 1,726 | -3% | -3% | -6% | | Measured and Indicated | 60,270 | 0.91 | 1,756 | 62,689 | 0.94 | 1,905 | -4% | -3% | -8% | | Island Gold District | | | | | | | | | | | Measured | 5,531 | 2.04 | 363 | 5,814 | 1.40 | 262 | -5% | 46% | 39% | | Indicated | 57,849 | 1.31 | 2442 | 59,008 | 1.18 | 2,244 | -2% | 11% | 9% | | Measured and indicated | 63,380 | 1.38 | 2,805 | 64,802 | 1.20 | 2,506 | -2% | 14% | 12% | | Inferred Gold Mineral Resources (exclusive of Mineral Reserves) | | | | | | | | | | | Island Gold | 2,449 | 16.88 | 1,329 | 7,106 | 16.52 | 3,774 | -66% | 2% | -65% | | Magino | 40,291 | 0.92 | 1,191 | 40,383 | 0.91 | 1,177 | 0% | 1% | 1% | | Island Gold District | 42,740 | 1.83 | 2,520 | 47,489 | 3.24 | 4,951 | -10% | -44% | -49% |

Mineral Resources reported are consistent with the CIM Definition Standards for Mineral Resources and Mineral Reserves Mineral Resources are reported at an assumed gold price of $1,800/oz Mineral Resources are not Mineral Reserves and do not have demonstrated economic viability. There is no certainty that all or any part of the Mineral Resources estimated will be converted into Mineral Reserves Island Gold underground Resources are estimated at a cut-off grade of 3.36 g/t Magino open pit Resources are estimated at a cut-off grade of 0.28 g/t Au Contained Au ounces are in-situ and do not include metallurgical recovery losses Mineral Resources are exclusive of Mineral Reserves Totals may not add up due to rounding Jeffrey Volk, CPG, FAusIMM, Director of Reserves and Resources for Alamos Gold Inc is the Qualified Person for the Magino open pit Mineral Resource estimate. Tyler Poulin, P. Geo., Geology Superintendent for Alamos Gold , is the Qualified Person for the Island Gold underground Mineral Resource estimate. Mr. Volk and Mr. Poulin are Qualified Persons within the meaning of Canadian Securities Administrator's National Instrument 43-101 ("NI 43-101")

Economic Analysis

The Base Case LOM Plan has an estimated base case after-tax NPV (5%) of $4.5 billion assuming a long-term gold price of $2,400 per ounce and USD/CAD foreign exchange rate of $0.75:1.

Assuming a $3,300 per ounce gold price, the after-tax NPV (5%) increases to $6.7 billion. The mine plan, operating parameters and capital estimates incorporated in the Base Case LOM Plan are effective as the first quarter of 2025. The project economics are sensitive to metal price assumptions and input costs as detailed in the tables below.

Island Gold District: Base Case LOM Plan After-Tax NPV (5%) Sensitivity ($ Millions)

| | -10% | -5% | Base Case | 5% | 10% | | Gold Price | $3,337 | $3,897 | $4,477 | $5,080 | $5,704 | | Canadian Dollar | $4,752 | $4,616 | $4,477 | $4,339 | $4,198 | | Capital Costs | $4,552 | $4,514 | $4,477 | $4,440 | $4,403 | | Operating Costs | $4,722 | $4,600 | $4,477 | $4,355 | $4,232 |

Island Gold District: Base Case LOM Plan After-Tax NPV (5%) Sensitivity to Gold Price

| Gold Price ($/oz) | After-Tax NPV 5% ($M) | | $2,000 | $2,942 | | $2,400 (Base Case 1 ) | $4,477 | | $2,750 | $5,098 | | $3,000 | $5,811 | | $3,300 | $6,667 | | $3,500 | $7,236 |

1. Base case includes a gold price of $3,000/oz in 2025 through to 2027, and a long-term (2028+) gold price of $2,400/oz

Base Case LOM Plan Overview

The Island Gold District is comprised of the Island Gold underground mine and the Magino open pit mine. Both operations will utilize the centralized Magino mill for processing ore and the Magino tailings management facility for tailings storage.

Underground ore from Island Gold is currently being processed through the Island Gold mill. During the third quarter of 2025, the Company expects to shut down the Island Gold mill and transition to processing both Island Gold and Magino ore through the Magino mill at a rate of approximately 11,200 tpd.

The Phase 3+ Expansion of Island Gold is expected to double underground mining rates to 2,400 tpd through the addition of a shaft and paste plant. Following completion of the expansion in 2026, underground mining will transition from trucking ore and waste to skipping ore and waste to surface, through the new shaft infrastructure. This is expected to drive production higher and costs significantly lower. The Magino mill will be expanded to 12,400 tpd to accommodate the increased production rates from Island Gold of 2,400 tpd, with the remaining 10,000 tpd coming from the Magino open pit.