PERPETUA RESOURCES CORP.

Summary Disclosure

The Company has only one material mining property, the Stibnite Gold Project, a formerly abandoned, brownfield mine site in rural Idaho, USA. We hold the Stibnite Gold Project through our wholly owned subsidiary Idaho Gold Resources Company, LLC.

The Company is currently focused on advancing the Project towards a full construction decision for the Project in 2026, including finalizing the remaining permits and securing project financing.

The Project includes mining the Yellow Pine, Hangar Flats and West End Deposits using conventional open pit methods, conventional processing methods to extract gold, silver and antimony, and on-site production of gold (“Au”) and silver (“Ag”) doré and an antimony (“Sb”) concentrate. An extensive reclamation and restoration program for certain historical legacy impacts to the Project site, including the recovery and reprocessing of historical tailings, restoration of fish passage during and after operations, relocation of historical mining wastes to engineered storage facilities, stream restoration, and reforestation of impacted areas, is included in the Project. Some environmental work has been completed under the ASAOC, which is designed to protect water quality on the Project site. Approvals from the U.S. EPA and USDA may be required with respect to environmental work at the site, including both activities pursuant to the Plan of Operations and work not currently included in the Project. Decommissioning the site includes progressive and concurrent remediation, reclamation, and restoration activities, beginning at the start of construction and continuing beyond the operations phase, through Project reclamation and closure.

Certain key milestones were completed in 2025. On January 3, 2025, the USFS issued its ROD approving the 2021 Modified Mine Plan that was analyzed in the FEIS. On May 19, 2025, the USACE issued its ROD for the CWA Section 404 permit. Following receipt of the USFS ROD and USACE ROD, the USFS approved the Plan of Operations, which is based on the ROD and the Modified Mine Plan, for the Project in October 2025. Upon placement of certain construction phase financial assurance and receipt of the required notices from USFS, IDL and USACE, the Company began early works construction for the Project on October 21, 2025.

Technical Report Summary

The disclosures in this “Item 2. Properties” regarding Perpetua Resources’ 100% interest in the Stibnite Gold Project have been prepared in accordance with the mining property disclosure rules specified in S-K 1300. Except for subsequent events or as otherwise noted, the disclosure in this Annual Report on Form 10-K of a scientific or technical nature for the Stibnite Gold Project is derived from, and in some instances is an extract from, the Technical Report Summary, dated as of December 31, 2025 (the “Technical Report Summary” or “TRS”).

The TRS updates, as of December 31, 2025, the information presented in the technical report titled “Stibnite Gold Project, S-K 1300 Technical Report Summary, Valley County, Idaho, USA” dated as of December 31, 2021, and amended as of June 6, 2022 (the “2022 TRS”). Updates since the 2022 TRS primarily relate to permitting, exploration drilling, engineering, land management, and financial analyses. The economic information included in the TRS is presented as of December 31, 2025, and updates the information presented in the 2022 TRS, which was supplemented by an updated cash flow model published by the company on February 13, 2025 (the “Financial Update”). The Financial Update applied cost estimates, commodity pricing and other assumptions as of the fourth quarter of 2025 and was based, in part, on basic engineering work completed in January 2025 by Ausenco Engineering USA South Inc. (“Ausenco”), and with contributions from other mining engineers and consultants. Since February 2025, the Company has continued to progress engineering, contracting, and early construction activities, and announced in December 2025 the appointment of Hatch Ltd. (“Hatch”) as EPCM contractor for certain design, engineering, procurement, construction, management, testing, studies, and related services for the Stibnite Gold Project, including the process plan, the pressure oxidation facility, associated on-site infrastructure, utilities, and facilities, together with overall integration, coordination, and execution support for those in-scope elements of the Project. Engineering, contracting and early works construction activities are ongoing, and may result in revisions to the costs, figures, methods and assumptions presented in the TRS as they progress.

The most notable updates from the 2022 TRS and the Financial Update include the following:

The TRS is included as Exhibit 96.1 of this Annual Report on Form 10-K and incorporated herein by reference. You should read the TRS as part of your review of the information in thisItem 2. Properties.

Certain capitalized terms in this section not otherwise defined have the meanings ascribed to them in the TRS.

Information of a scientific or technical nature in this Annual Report have been approved by Christopher Dail, AIPG CPG #10596, Exploration Manager for Perpetua Resources Idaho, Inc. and James Norine, P.E., Senior Vice President, Projects for Perpetua Resources Idaho, Inc. and each meet the qualifications to be a “qualified person” as defined in S-K 1300.

Assumptions

Portions of the information presented in this Annual Report on Form 10-K and the information contained in the TRS rely on a number of estimates and assumptions, including estimates and assumptions which are inherently subject to significant scientific, business, economic and competitive uncertainties and contingencies that could be material should those assumptions be incorrect. These assumptions include, but are not limited to, certain assumptions as to capital costs, production rates, operating costs, recovery and timing of construction and production; assumptions that the current price and demand for gold and other metals will be sustained or will improve; assumptions that the equipment and personnel required for permitting, construction and operations will be available on a continual basis; there are no significant errors in calculations and information used in mineral resource and reserve estimates; there will be no unforeseen delays, unexpected geological or other effects, equipment failures, or significant permitting delays; and that the Corporation will be able to source funding for construction and operations when required and on acceptable terms. For a description of the key assumptions, parameters and methods used to estimate mineral reserves and mineral resources included in this Annual Report on Form 10-K, as well as data verification procedures and a general discussion of the extent to which the estimates may be affected by any known environmental, permitting, legal, title, taxation, sociopolitical, marketing or other relevant factors, please review the TRS, which is included as an exhibit to this Annual Report on Form 10-K. The cost estimates and assumptions contained in the TRS are dated as of December 31, 2025, and use cost estimate and commodity pricing that are current as of December 31, 2025. Ongoing efforts to advance engineering, contracting and construction work may result in revisions to the costs, figures, methods and assumptions presented. See “Item 1A. Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” for a discussion of additional industry and business risks and assumptions.

Economic Highlights 1

The Stibnite Gold Project economics, as contemplated in the TRS, are summarized in the table below.

Economic Sensitivities 1

The base case for economic analysis was prepared using consensus average pricing of $3,250/oz gold, $10.00/lb antimony, and $40.00/oz silver, which was based on a broad range of investment bank forecasts as of December 2025.

The Company has also prepared Cases B, C, and D, which were developed to illustrate the Stibnite Gold Project’s economic sensitivity to a range of metal price assumptions. Each of these is presented in the table below and prepared on the same basis as the TRS, except with respect to commodity prices.

The prices used in the TRS and in this Annual Report are consistent with accepted industry practices, analyst forecasts, and the range of prices being used for other project studies for gold and silver.

There is no guarantee that the gold, silver, and antimony prices used in the study cases would be realized at the time of production. Prices could vary higher or lower with a corresponding impact on Project economics. The Company’s mineral reserves and mineral resources continue to be estimated based on $1,600/oz and $1,500/oz gold prices, respectively, as set forth in the TRS.

Property Description and Location

The Project location is in central Idaho, USA approximately one hundred (100) miles (“mi”) northeast of Boise, Idaho, thirty-eight (38) mi east of McCall, Idaho, and approximately ten (10) mi east of Yellow Pine, Idaho. Mineral rights controlled by Perpetua Resources include patented lode claims, patented mill sites, unpatented federal lode mining claims, and unpatented federal mill sites and encompass approximately 29,340 acres (forty-six (46) square miles). The claims are 100% owned, except for surface rights on portions of six (6) patented mill site claims held by a third party and twenty-seven (27) patented lode claims that are held under an option to purchase.

Effective May 9, 2013, Perpetua Resources granted a 1.7% NSR royalty on future gold production from the Project properties to FNIC. This royalty does not apply to production of antimony and silver. The royalty agreement applies to all patented and unpatented mineral claims, except for the Cinnabar claim group where PRII holds an option to purchase but would be extended to the Cinnabar

claim group where the OTP exercised. In March 2024, a wholly owned subsidiary of Perpetua Resources sold FNIC a 100% royalty on the future payable silver production from the Project which would become effective in year seven after commercial production commences.

Stibnite Gold Project Location

Land Status Map

Mineral Concession Summary

Notes*:*

Patented Lode Claims and Patented Mill Sites

On June 11, 2009, a predecessor to SGC acquired and exercised an option to purchase (“OTP”) the Meadow Creek group of nine patented lode claims totaling approximately 184 acres from Bradley Mining Co. (“Bradley”).

A predecessor to IGRCLLC secured an OTP agreement from the J.J. Oberbillig Estate (the “Oberbilllig OTP agreement”) on June 2, 2009, to acquire 30 patented mill site claims totaling approximately 149 acres and six patented lode claims totaling approximately 124 acres. The Oberbillig OTP agreement was exercised and title to property rights were acquired on June 2, 2015. An associated transaction included the purchase and extinguishment of a 5% Net Smelter Return (“NSR”) royalty to the Oberbillig estate covering certain lands within the Project area. The majority of the mineralization constituting the West End Deposit is located within portions of these patented lode claims. Hecla Mining Company (“Hecla”) retains surface rights on portions of six of the patented mill sites but no mineral rights and IGRCLLC has a right to use the surface for various purposes and holds a right of first refusal should those surface rights be offered for sale. The Company is exploring alternatives with respect to this property, which may include acquiring such property from Hecla. While there is no certainty that a transaction will be finalized, the Company believes that if it is unable to purchase this surface property, that outcome will not have a material effect on the Company’s ability to develop the Project.

An OTP for patented lode mining claims covering portions of the Yellow Pine Deposit was conveyed to Perpetua Resources by way of a company merger between a predecessor to IGRCLLC and a subsidiary of Vista Gold Corp. that was agreed to February 22, 2011. The OTP for the subject patented claims was exercised on November 28, 2012. As a result of the merger, the predecessor to IGRCLLC became a wholly owned subsidiary of Perpetua Resources. The Yellow Pine claim group includes 17 patented lode mining claims totaling approximately 301 acres and eight unpatented lode mining claims.

On April 28, 2011, a predecessor to SGC purchased 6 patented lode claims east of the Project area. This group of claims is referred to as the Fern claim group, totaling approximately 100 acres.

Unpatented Federal Lode Mining Claims and Unpatented Federal Mill Site Claims

A subsidiary of a predecessor to IGRCLLC acquired 229 federal unpatented claims by purchase from previous owners in 2009 and 2011. These included 46 federal mill site claims and 183 federal unpatented lode mining claims. In addition to the purchased claims,

IGRCLLC predecessors or subsidiaries acquired by staking an additional 36 federal unpatented lode mining claims in 2009, 217 lode claims in 2010 and 901 federal unpatented lode-mining claims in 2011, and one federal unpatented lode mining claim in 2012. An additional 126 unpatented lode claims were staked in 2015. Minor modifications, including amended claim locations and changes in some claims have occurred since original staking and/or acquisition.

In 2021, SGC merged with IGRCLLC becoming the sole surviving entity and landowner of patented and unpatented mining claims and mill sites and various optioned properties. As of December 31, 2025, IGRCLLC owns 1,674 unpatented lode mining and mill sites totaling approximately 28,482 acres (11,526 hectares).

Maintenance of unpatented federal claims requires that IGRCLLC provide a list of claims and serial numbers to the Bureau of Land Management along with annual maintenance fees, currently $200 for each lode-mining claim or mill site on or before September 1st each year. This was completed for the most recent filing year. There are no underlying royalties on the federal lode-mining claims and mill sites other than the FNIC royalties. None of the claims are subject to back-in rights; however, FNIC holds a right of first refusal should mining claims, mill sites or other mineral properties be relinquished. Property taxes are paid annually for the patented lode mining claims and mill sites and are current. Routine maintenance and claim adjustments have occurred periodically since the inception of land acquisitions as required.

Stibnite Gold Logistics Facility

On September 9, 2016, IGRCLLC agreed to purchase an undeveloped 25-acre property in fee simple from private interests. The property is situated in Section 7, Township 14N, Range 5E, Boise Meridian. The sale closed on October 26, 2016. The property’s metallic and non-metallic mineral rights, apart from aggregate materials needed for construction purposes on the property, were retained by the previous owners.

The property, in an area known locally as Scott Valley, has frontage on the Cascade-Warm Lake Highway and was purchased to serve as a project logistics facility. The agreement provides for maintenance of certain pre-existing rights-of-way, easements and rights, none of which would be expected to inhibit use of the property for the intended purposes. PRII applied for a Conditional Use Permit from the Valley County Planning and Zoning Commission for the Scott Valley Logistics Facility which was granted on October 5, 2020.

Royalties, Option Agreements and Encumbrances

Option Agreements

On May 3, 2011, a predecessor to Perpetua entered into an OTP 27 patented lode claims totaling approximately 485 acres from the J.J. Oberbillig Estate (the Cinnabar option claims). This agreement was modified in an Amended and Restated Real Property Purchase Agreement effective December 1, 2016 (the “amended agreement”). The amended agreement also includes an assignment of the right of first refusal to purchase the surface rights associated with portions of certain patented mill site claims that J.J. Oberbillig Estate sold to Hecla under a Real Estate Purchase and Sale Agreement effective December 30, 2002. The right of first refusal for the Hecla tracts includes fixed terms should Hecla decide to sell the parcel. Perpetua has since obtained Hecla’s acknowledgment of the assignment of the right of first approval from the J.J. Oberbillig Estate to the Company. The amended agreement also includes granting of a renewable easement for a communications tower. Perpetua Resources is obligated to make payments to maintain the OTP to obtain title to these claims. The OTP has annual payments and can be extended up to 10 years after the original term of the agreement expires, through December 1, 2037, for additional consideration.

On December 10, 2019, a Perpetua Resources subsidiary entered into an option agreement to purchase 3.74 acres from private interest for an electrical switching station site. The OTP has a biannual payment of $2,500 through 2033.

Royalty Agreement

Effective May 9, 2013, Perpetua Resources and its subsidiaries granted a 1.7% NSR royalty on future gold production from the Project properties to FNIC, subject to adjustment based on final permitted capacity. The royalty does not apply to production of antimony and silver. The royalty agreement applies to all patented and unpatented mineral claims, except for the Cinnabar option claims where Perpetua Resources holds an OTP. Under the agreement, FNIC has the right, but not the obligation, to extend the property subject to the royalty to the Cinnabar option claims upon notice that the OTP is exercised by Perpetua.

On March 21, 2024, Perpetua Resources and its subsidiaries granted a 100% NSR royalty on the future payable silver production from the Project to FNIC. The silver royalty agreement applies to the same properties as the gold royalty. The silver royalty agreement provides a mechanism whereby FNIC can receive minimum payments equal to 100% of the payable silver from the sale of doré commencing in the seventh calendar year following commercial production and ending upon the completion of the fifteenth calendar year following commercial production. The silver royalty agreement also provides FNIC an option upon the occurrence of certain conditions precedent (including achieving commercial production) to pay the Company a contingent payment and receive a royalty on any silver payable from the production of antimony concentrate from the Project. The Company’s obligations under the gold and silver royalty agreements are secured by a continuing security interest and a first priority lien on certain collateral including the land and mineral interests comprising the Project.

Geologic Setting and Mineralization

Bedrock in the region can be subdivided into the pre-Cretaceous metasedimentary “basement,” the Cretaceous Idaho Batholith, Tertiary intrusions and volcanics, and Quaternary unconsolidated sediments and glacial materials. The Stibnite Gold Project is situated along the eastern edge of the Idaho Batholith, on the western edge of the Thunder Mountain caldera complex and within the Central Idaho Mineral Belt.

Large, north-south striking, steeply dipping structures exhibiting pronounced gouge and multiple stages of brecciation occur in the district and are often associated with east-west and northeast-southwest trending splays and dilatant structures.

The Yellow Pine and Hangar Flats deposits are hosted primarily by intrusive phases of the Idaho Batholith along the Meadow Creek Fault Zone. The West End Deposit is hosted primarily by Neoproterozoic to Paleozoic metasedimentary rocks of the Stibnite roof pendant along the West End Fault Zone.

Mineralization and alteration in the district are associated with multiple hydrothermal alteration events occurring through the Paleocene and early Eocene epochs. Main-stage gold mineralization and associated potassic alteration typically occurs in structurally prepared zones. The gold is associated with very fine grained disseminated arsenical pyrite and arsenopyrite to a lesser extent. The gold almost exclusively exists in solid solution in these minerals. Antimony mineralization occurs primarily as the mineral stibnite. Additional gold mineralization affecting rocks of the Stibnite roof pendant (i.e. the West End Deposit) is associated with epithermal quartz-adularia-carbonate veins.

Deposits of the district are not readily categorized based on a single generic deposit model due to complexities associated with multiple overprinting mineralization events and uncertainties regarding sources of mineralizing hydrothermal fluids.

Permits

The Project was subject to formal review by the USFS and the Army Corps under NEPA and by other state and federal agencies under various laws requiring permits. Pursuant to NEPA, on September 6, 2024, the USFS published its Final Environmental Impact Statement and a Draft Record of Decision (ROD), which commenced a pre-decisional objection and resolution period. On January 3, 2025, the USFS issued its ROD approving the 2021 Modified Mine Plan. Per the requirements of the ROD, numerous plans comprising the suite of Environmental Monitoring and Management Plans were completed to incorporate Project updates, mitigation measures, environmental protection measures, and design features. In September 2025, the Company submitted its Plan of Operations, which was based on the 2021 Modified Mine Plan and incorporated requirements from the ROD and various plans, including the Environmental Monitoring and Management Plans. On October 20, 2025, USFS approved and signed the Plan of Operations and also approved the construction phase financial assurance submitted by the Company.

Following the USFS’ publication of the ROD for the Project in January 2025, claims were filed in the U.S. District Court for the District of Idaho against the USFS and other federal agencies on February 18, 2025 by a number of claimants, including Save the South Fork Salmon and the Idaho Conservation League, alleging violations of NEPA and other federal laws in the regulatory review process. Among other remedies, the claimants seek to vacate the ROD, Final Biological Opinions and other Project approvals and enjoin any further implementation of the Project. PRII has filed a motion with the court to intervene in this lawsuit granted on April 2, 2025.

On August 29, 2025, the Nez Perce Tribe filed a separate lawsuit against the USFS and other federal agencies in the United States District Court for the District of Idaho the challenging the USFS ROD and other approvals by the USFS and other federal agencies in connection with the Stibnite Gold Project and alleging violations of NEPA and other federal statutes, regulations, rules and requirements in the regulatory review and approval process in of the Project. Among other remedies, the Tribe seeks to vacate the USFS

ROD and other Project approvals and to enjoin any further implementation of the Project. PRII filed a motion to intervene in this lawsuit, which was granted by the District Court on September 4, 2025.

The Idaho Board of Environmental Quality (“IBEQ”) published an order on May 27, 2025 upholding the air permit to construct (“PTC”) issued for the Project by the Idaho Department of Quality (“IDEQ”) in June 2022 and denying certain petitioners’ appeal from various administrative proceedings with respect to the PTC. Thereafter, the petitioners filed a petition for judicial review in the Idaho state district court for the County of Ada against the IBEQ, IDEQ, and Perpetua Resources alleging the PTC violates applicable law and seeking to set aside the PTC.

The foregoing lawsuits in federal and state court remain pending. The Company believes the challenged federal and state regulatory processes were conducted thoroughly and completely by the relevant regulatory agencies. However, there can be no assurance that the Project permits and other regulatory approvals will be upheld upon judicial review.

Review of the Company’s CWA Section 404 permit application, proposed Compensatory Mitigation Plan, and associated financial assurance was completed by the U.S. Army Corps of Engineers and its CWA Section 404 permit and the associated ROD was issued May 19, 2025 based on the same FEIS as the USFS.

The Company has been able to obtain and advance work on multiple permits from agencies of the State of Idaho in connection with the Project. The relevant agencies are at various stages of reviewing and approving the Company’s applications under state law. Certain of the permits and other regulatory authorizations are subject to contested administrative proceedings under Idaho statutes and regulations. Work on and updates to other required ancillary permits, management and mitigation plans, financial assurance, and other permitting requirements will continue throughout the duration of construction and through operations.

For additional detail regarding the NEPA and permitting processes and the status of various activities thereunder, including ongoing lawsuits and administrative proceedings challenging the USFS ROD and other permits and regulatory authorizations for the Project, seeItem 1. Business – Permitting and Environmental Matters; Item 3. Legal Proceedings; and “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations – Ancillary Permitting Update Ancillary Permitting Update,” below.

Exploration

The Project area and the surrounding district has been the subject of exploration and development activities for over 100 years, yet much of the area remains poorly explored due to its remote location, poor level of outcrop and extensive glacial cover. Perpetua Resources has completed extensive exploration work since 2009 that has included: geophysics; rock, soil and stream sampling and analysis; geologic mapping; mineralogical and metallurgical studies; and drilling.

This newer data has been integrated with datasets from previous operators and provides a comprehensive toolkit for future exploration. These efforts have led to the identification of over 75 prospects with varying levels of target support. These prospective areas include targets within, under, and adjacent to existing deposits; bulk mineable prospects along known or newly identified mineralized trends; high grade underground targets and early-stage greenfield prospects and conceptual targets based on geophysics or geologic inference.

Exploration targets include conceptual geophysical targets, geochemical targets from soil, rock and trench samples, and results from widely spaced drill holes; as a result, the potential size and tenor of the targets are conceptual in nature. There has been insufficient exploration to define mineral resources on these prospects and this data may not be indicative of the occurrence of a mineral deposit. Such results do not provide assurance that further work will establish sufficient grade, continuity, metallurgical characteristics, and economic potential to be classed as a category of mineral resource. Mineral resources are not mineral reserves and do not have demonstrated economic viability.

The Project area, including the three main deposits, has been drilled by numerous operators, totaling 825,963 ft in 2,864 drill holes, of which Perpetua Resources drilled 778 holes totaling over 376,389 ft since 2009. Pre-Perpetua Resources drilling was undertaken by a wide variety of methods and operators while Perpetua Resources employed a variety of drilling methods including core, reverse circulation, auger, and sonic throughout the district, but with the primary method being core. Operators who conducted significant exploration and/or mineral extraction during this era included: United Mercury Mines. Yellow Pine Company, Bradley Mining Company, Louisiana Land and Exploration Company, Canadian Superior Mining (U.S.) Ltd., El Paso Oil and Gas, Rancher’s Exploration Company, Twin Rivers Exploration, MinVen Corporation, Pioneer Metals Corporation, Hecla Mining Company, Barrick Gold Corporation (formerly American Barrick Resources), Stibnite Mine Inc., and Dakota Mining Company.

During the fourth quarter of Q4 2025 a short exploration and geotechnical core drilling program was initiated and continued through the beginning of Q1 2026. A total of 4 exploration and 15 geotechnical holes were completed with a cumulative 9136 feet completed. Logging and sampling of the drill holes were in progress at the effective date of this report.

Mineral Resources and Mineral Reserves Estimates

The tables below present the estimated Mineral Resources and Mineral Reserves for the Project at December 31, 2025 presented in accordance with S-K 1300. There were no changes in reported Mineral Resources and Mineral Reserves reported for the years ended December 31, 2025 and 2024.

Mineral Resource Estimates

The following table presents the estimated Indicated and Inferred Mineral Resources for the Project at December 31, 2025 based on $1,500/oz gold price and are presented exclusive of Mineral Reserves in accordance with S-K 1300. There were no changes to Mineral Resources since December 31, 2024.

Consolidated Mineral Resource Statement for the Stibnite Gold Project at December 31, 2025, based on $1,500/oz gold, EXCLUSIVE OF RESERVES:

Notes:

Mineral Reserve Estimates

The following table presents the estimated Mineral Reserves for the Project at December 31, 2025 based on $1,600/oz gold price and presented in accordance with S-K 1300. There were no changes to Mineral Reserves since December 31, 2024. Under S-K 1300, a Proven Mineral Reserve is the economically mineable part of an indicated and, in some cases, a measured mineral resource and a Probable Mineral Reserve is the economically mineable part of a measured mineral resource and can only result from conversion of a measured mineral resource.

Mineral Reserves Summary (Metric Units) at December 31, 2025 based on $1,600/oz gold:

Notes:

Mineral Reserves are reported from the reference point of delivery to the processing plant. These reserves are subject to variable metallurgical recoveries for gold, silver, and antimony depending on the host rock, process flowsheet, and product (i.e. doré bullion or antimony concentrate). The average recoveries into bullion are 87% for gold and 13% for silver. The average recoveries into antimony concentrate are 68% for antimony, 0.1% for gold, and 2% for silver.

All numbers have been rounded in above table and may not sum correctly.

Mining Methods

The mine plan developed for the Project incorporates the mining of the three in situ deposits: Yellow Pine, Hangar Flats, and West End and their related development rock; and the re-mining of Historical Tailings along with its cap of spent heap leach ore. The mine plan, including the mine features, mining methods, process and recovery methods, and infrastructure, are based on the 2021 Modified Mine Plan which was approved by the USFS in January 2025 in its final Record of Decision and was incorporated by the Company in its Plan of Operations that was approved by the USFS in October 2025.

The general sequence of open pit mining would be Yellow Pine deposit first, Hangar Flats deposit second, and West End Deposit last. This sequence generally progresses from mining highest value ore to lowest value ore and accommodates the sequential backfilling of the Yellow Pine and Hangar Flats open pits with material mined from West End open pit. Lower grade ore extracted during mining of the three pits is stockpiled and then processed during the operating life of the mill. The spent ore that overlies the Historical Tailings would be used as tailings storage facility (“TSF”) construction material and is treated as stripping. Most development rock would be sent to one of five destinations: the TSF embankment, the TSF buttress, the Yellow Pine pit as backfill, the Hangar Flats pit as backfill, or the Midnight area within the West End pit as backfill. The Historical Tailings would be hydraulically transferred to the process plant during the first four years of operation, concurrent with mining and processing ore from the Yellow Pine open pit.

Mining at the Stibnite Gold Project would be accomplished using conventional open pit hard rock mining methods with a production fleet consisting of two 28-yd3 hydraulic shovels, three 16-yd3 wheel loaders, and a fleet of approximately twenty 150-ton haul trucks. Mining is planned to deliver 7.30 M tonnes of ore to the crusher per year (nominally 20 k tonnes per day) and approximately 22.1 M tonnes of development rock per year to DRSFs. Pre-stripping the open pits would begin two years prior to ore processing and open pit mining would continue until year 12 of operation. Once open pit mining is completed, the mining fleet will continue to provide ore to the mill from ore stockpiles until approximately the end of the first quarter in year 15. A total of 102 M tonnes of ore would be mined from the three open pits and an additional 2.7 M tonnes of historic tailings would be mined. Approximately 254 M tonnes of development rock would be mined from the three open pits for a total of 356 M tonnes mined from the open pits and an average strip ratio (waste:ore) of 2.5.

Long-term lower-grade ore stockpiles have been incorporated into the mine plan located for the most part within the footprint of the TSF buttress, thereby minimizing their incremental disturbance. The primary benefits to adding ore stockpile capacity are increased potential to optimize process ore feed value throughout the mine life, improved utilization of the Mineral Resource, reduced peak water treatment needs, reduced development rock tonnage and associated mining impacted water management. The stockpiling strategy is particularly significant during the first half of the mine life when Yellow Pine high value ore is mined at a rate greater than process plant throughput capacity. If stockpile capacity is not available, either the period-based cut-off value must increase resulting in ore converted to waste, or the mining rate reduced to align with process plant throughput capacity resulting in deferred access to high-value ore deeper in the open pit. The addition of long-term ore stockpiles allows for relatively high value ore mined from Yellow Pine open pit to be stockpiled and made available to process when lower value ore is being mined in West End open pit.

Recovery Methods

The process flowsheet for most of the Yellow Pine, Hangar Flats, and West End material uses bulk sulfide flotation to maximize recovery of gold to a sulfide concentrate amenable to treatment by pressure oxidation for materials assaying less than 0.1% antimony. High antimony materials would be first subject to a selective antimony flotation process, thereby producing a shippable antimony concentrate, with a gold-bearing bulk sulfide rougher concentrate to be floated from the antimony flotation tailings. Some of the oxidized West End ores are more transitional or free milling in nature, and an ore leaching process was developed to treat these materials. Testing was also conducted on samples of the historical (Bradley) tailings. This work showed the historical tailings could be processed using the same flowsheet as, and most likely as a blend with fresh sulfide ores. A revised set of flotation models was developed for all ore bodies during the 2024 basic engineering studies. These models were developed using test results from the historical test work programs and improved the predictability of the metallurgical performance.

Projected gold, silver and antimony recoveries vary by lithology, metal grade, sulfur content, mineralogy and oxidation state. Projected life of mine metal recoveries from low-antimony materials to a pyrite flotation concentrate averages 87.1% gold, 8% silver and 0% antimony. Projected life of mine metal recoveries for high-antimony materials to antimony sulfide concentrates average 71.6% antimony, 10.1% silver and 0.66% gold. Low reported antimony recovery for antimony reporting to the pyrite concentrates and low reported gold recoveries for gold reporting to the antimony concentrates are the result of misplacement of small amounts of antimony and gold bearing mineral phases to the respective concentrates. Sulfide material will be processed by flotation, concentrate pressure oxidation and cyanide leaching of the concentrate; transition material will be treated similarly; however, the flotation tailings will also be leached; oxide materials will be whole ore leached through the oxide leach circuit. West End sulfide material is refractory while transition material has a significant free milling gold content.

The pressure oxidation testing confirmed consistent gold recoveries in the 96.5-99.0% range. The Project’s process plant has been designed to process sulfide, transitional and oxide material from the Yellow Pine, Hangar Flats, and West End Deposits. The processing facility is designed to treat an average of 20,000 tonne/d, or 7.3 Mt/y. Additionally, the Historical Tailings would be reprocessed early in the mine life to recover precious metals and antimony, and to provide space for the TSF embankment and buttress.

The process operations include crushing, grinding, antimony and gold flotation, pressure oxidation, leaching and carbon-in-pulp (“CIP”) recovery, cyanide detoxification, carbon handling and pressure stripping, precious metal electrowinning, mercury retort removal, and doré bar production. Auxiliary operations include a plant to supply oxygen to the autoclave, leach, and detox circuits, and limestone mining, crushing, grinding, and calcination processes to provide limestone slurry and milk of lime products. A leaching, CIP recovery, and detoxification process is planned for late in the mine life to process crushed and ground oxide material and recover gold from the tailings of transitional (mixed oxide-sulfide) material. Two finished products from the Stibnite Gold Project ore processing facility will be doré bars and antimony‐silver concentrate. The design of the Project’s processing facility remains in active development and will continue to be refined as detailed engineering progresses. Updates may be required to reflect new technical specifications, optimization studies, permitting requirements and outcomes from ongoing procurement and contracting activities.

Infrastructure

The Project will require upgrades to existing offsite infrastructure such as roads and power supply, as well as onsite and offsite infrastructure additions such as worker accommodations, water management systems, and tailings management systems.

Site Access

The site is currently accessed by the Stibnite Road, (National Forest road NF-412), from the village of Yellow Pine, with three alternative routes up to that point. Alternative access via the Burntlog Route was developed over several other possible alternatives because it provides safer year-round access for mining operations, reducing the proximity of roads to major fish-bearing streams, and this route respects the advice and privacy of community members close to the Project location. The route originates from the intersection of Highway 55 and Warm Lake Road and is approximately 71 miles long. The route consists of 34 miles of existing highway (Warm Lake Road), 23 miles of upgraded road, and 14 miles of new road. The 37 miles of new and upgraded road has a design speed of 20 mph, maximum 10% grade, a 21-foot width, and intermediate-sized tractor trailer loading criteria. A maintenance facility would be constructed along the route.

A through-site access route will replace the current access through the Stibnite Gold Project site during mine operations. A new 16-foot-wide gravel road is planned to provide access from Stibnite Road to Thunder Mountain Road through the mine site.

Logistics Facility

The offsite administrative offices, transportation hub, and warehousing needed for the Project, referred to as Stibnite Gold Logistics Facility (“SGLF”), will be located on private land in Valley County, with easy access to State Highway 55. The administration building will include offices for managers, safety and environmental services, human resources, purchasing and accounting personnel. Operating supplies for the mine will be staged and consolidated at the SGLF to reduce traffic to the site.

Power Supply and Transmission

Grid power planned for the Project needs to be upgraded to support the approximately 65-megawatt (MW), 72MVA load including upgrading approximately 63 miles of existing powerlines to 138 kV and approximately 9 miles of new 138 kV line. The 138-kV line would be routed to the Project’s main electrical substation where transformers would step the voltage down to the distribution voltage of 34.5 kV.

Worker Accommodations

A new worker housing facility (camp) is planned approximately 2 miles south of the ore processing plant area to provide accommodations for most of the construction workforce and for the operations workforce. Leased accommodation units are planned during peak construction activity and would be demobilized following construction since the peak construction accommodation requirements (approximately 1,050 workers) are much greater than the operations requirements of approximately 650 workers on the Project site.

Water Management

Perpetua Resources has planned a water management system that protects or improves water quality in Project-area streams and provides water for ore processing, fire protection, exploration activities, surface mining (dust control), and potable water needs. These water management activities are subject to conditions imposed pursuant to the Modified Mine Plan approved by the USFS in the ROD and Plan of Operations and related regulatory documentation issued under NEPA and to water rights granted to Perpetua pursuant to an order of the IDWR. Additional permits required to be obtained for the Project may affect the Company’s water management activities. See “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations – Ancillary Permitting Activities” below for additional information relating to certain state permits involving water management and their current status.

The key water management consideration for the Project site is the large amount of snowmelt runoff during the months of April through June, making spring melt the critical time for water management, storage, and treatment. Surface water that has the potential to introduce mining- and process-related contaminants (contact water) will be kept separate from surface water that originates from undisturbed, uncontaminated ground (non-contact water). This will be accomplished by diverting clean water around mine facilities and collecting and reusing, evaporating, or treating and discharging contact water.

The water needed for ore processing is planned to come from meteoric and tailings consolidation water reclaimed from the TSF, water from pit dewatering, contact water, groundwater wells, and a surface intake near the upstream portal of the East Fork South Fork Salmon River (“EFSFSR”) diversion tunnel. Contact water from the pits, stockpiles, TSF buttress, truck shop, ore processing facilities, and legacy materials exposed during construction would be collected in lined ponds or in-pit sumps for later use in ore processing, dust control, or treatment for discharge. Excess dewatering water not used for ore processing would be treated, if required, and discharged to a surface outfall.

Major water diversions include construction of a tunnel and fishway to divert the EFSFSR and provide fish passage around the Yellow Pine pit, and surface diversions of Meadow Creek at the TSF, TSF Buttress, and Hangar Flats pit. Other smaller scale diversions are provided to intercept hillslope runoff and minor tributaries at the TSF, TSF Buttress, Fiddle GMS, Bradley Tailings reprocessing operation, open pits, and process plant area.

Tailings Management

The Project is projected to produce approximately 120 million short tons of tailings solids. The tailings would contain trace amounts of cyanide and metals (including arsenic and antimony), so a fully lined containment facility utilizing a composite liner with a leak collection/recovery system is proposed to isolate the tailings and process water.

The TSF would consist of a rockfill embankment, a fully lined impoundment, and appurtenant water management features including a surface diversion of Meadow Creek and its tributaries around the facility. The TSF Butress located immediately downstream of, and abutting against, the TSF embankment would substantially enhance embankment stability. Historical spent heap leach ore would be reused in TSF construction, in locations isolated from interaction with water, but the majority of the rockfill would be development rock sourced from the open pits. Design criteria were established based on the facility size and risk using applicable dam safety and water quality regulations and industry best practice for the TSF embankment on a standalone basis; the addition of the buttress substantially increases the safety factor for the design. The TSF impoundment, embankment, and associated water diversions would occupy approximately 423 acres at final buildout, with an approximately 480-foot ultimate height.

Capital and Operating Costs

Capital expenditures or capital costs (“CAPEX”) and operating expenditures or operating costs (“OPEX”) estimates as of December 31, 2025 were developed in connection with the completion of Basic Engineering and ongoing Detailed Engineering Work, and are presented in the TRS based on fourth quarter 2025, un-escalated U.S. dollars. The CAPEX and OPEX estimates were developed based on fourth quarter 2025, un-escalated U.S. dollars. Vendor quotes were obtained or updated for all major equipment to account for inflation or price changes. Most costs were developed from first principles, although some were estimated based on factored references and experience with similar projects elsewhere. Vendor quotes were obtained for all major equipment and operating consumables. The CAPEX and OPEX estimates are forward-looking statements and remain subject to the risks and uncertainties set forth in the section titled “Cautionary Note Regarding Forward-Looking Statements” at the beginning of this Annual Report.

Capital Costs

This CAPEX estimate includes three components: (1) the initial CAPEX to undertake the detailed design, pre-strip, construction, and commissioning of the mine, plant facilities, ancillary facilities, utilities, and operations camp, and complete on and

offsite environmental mitigation and remediation; (2) the sustaining CAPEX for facilities expansions, mining equipment replacements, expected replacements of process equipment and ongoing environmental mitigation activities; and (3) the closure and reclamation CAPEX to close and rehabilitate on and off-site components of the Project, which includes post-closure water treatment. Closure assumes self-performed closure costs, which may differ from those assumed for financial assurance calculations required by regulators. The CAPEX estimate includes direct mining equipment and pre-stripping costs, process plant costs, on-site infrastructure such as the TSF and the operations camp, and off-site infrastructure such as the power transmission line, the mine access road, the Stibnite Gold Logistics Facility (SGLF), and reclamation and closure costs. The initial CAPEX also includes indirect costs for detailed design and engineering, land acquisition, some environmental mitigation, and other costs. Initial CAPEX also includes an estimate of contingency based on the accuracy and level of detail of the cost estimate. The purpose of the contingency provision is to make an allowance for uncertain cost elements that may occur but are not included in the cost estimate. These cost elements include uncertainties concerning completeness, accuracy and characteristics or nature of material takeoffs, accuracy of labor and material rates, accuracy of labor productivity expectations, and accuracy of equipment pricing. The CAPEX estimates are considered to have an accuracy range of -10% to +15%.

The table below provides a summary of CAPEX estimates for the Project.

Operating Costs and All-In Costs

The Project OPEX estimate includes mine operating costs, process plant operating costs, and general and administrative (“G&A”) costs. Cash costs, expressed in dollars per short ton ($/st) milled or dollars per troy ounce of gold ($/oz Au) produced, are typically expressed before and after by-product credits (from antimony concentrate sales). Total cash costs include smelting and refining charges, transportation charges, and royalties. The All-In Sustaining Costs (“AISC”) and the All-In Costs (“AIC”) include non-sustaining CAPEX, and closure and reclamation CAPEX, respectively. A summary of these Project costs is presented below. The assumptions that were used to estimate OPEX are presented in the TRS. Cash Costs, Total Cash Costs, AISC, and AIC are projected non-GAAP financial measures and are not historical measures of financial performance and are not presented in accordance with GAAP. For more information regarding financial measures not prepared in accordance with GAAP, see “Non-GAAP Financial Measures” at the end of Item 2. These non-GAAP measures are forward-looking statements and remain subject to the risks and uncertainties set forth in the section titled “Cautionary Note Regarding Forward-Looking Statements” at the beginning of this Annual Report.

Mineral Resource and Reserve Internal Controls

Perpetua Resources’ field work on the Project from 2009 to 2025, including drilling, was carried out under the supervision of Christopher Dail, CPG and Richard Moses, CPG, who were Perpetua Resources’ senior geologists responsible for certain aspects of the programs during the periods they were employed by Perpetua Resources. Field work, including drilling, completed in 2015-2017 was carried out under supervision of Kent Turner, independent senior geology consultant, and Austin Zinsser, Perpetua Resources’ Senior Resource Geologist and SME-Registered Member. The general mineral resource estimation methodology for all deposits, as noted in the TRS, involved the following procedures:

Quality Assurance/Quality Control program results do not indicate any problems with the analytical programs. Independent data audits have been conducted and indicate that the sample collection and database entry procedures are acceptable. All core samples have been catalogued and stored in designated areas.

Mineral resources and mineral reserves are estimates that are imprecise and depend upon geologic interpretation and statistical inferences drawn from drilling and sampling analysis, which may prove to be unreliable. See “Item 1A. Risk Factors – Perpetua Resources’ mineral resource and mineral reserve estimates may not be indicative of the actual gold or other minerals that can be mined.”

Non-GAAP Financial Measures

To provide investors with additional information in connection with our economic analysis as determined in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”), we disclose certain projected non-GAAP financial measures. The projected non-GAAP financial measures include expected Cash Costs, Total Cash Costs, AISC, AIC, Average Annual EBITDA and Annual Average Free Cash Flow (“FCF”) with respect to the expected results of the Project as presented in the TRS.

We define “Cash Costs” as the sum of mining costs, processing costs, mine-level G&A and by-product credits; “Total Cash Costs” as the sum of Cash Costs, royalty costs, treatment costs, refining costs, and transportation costs; we define “All-In Sustaining Costs” as the sum of Total Cash Costs and sustaining capital costs (all costs required to sustain operations); we define “All-In Costs” as the sum of AISC, non-sustaining capital costs, and closure and reclamation capital costs; we define earnings before interest, taxes and depreciation and amortization (“EBITDA”) as total revenue minus operating costs, offsite charges and royalties; we define “Free Cash Flow” as EBITDA as adjusted for changes in net working capital, all capital expenditures (initial, sustaining, and closure capital expenditures), and salvage value; and we define After-Tax FCF as FCF less taxes payable. FCF does not entirely represent cash available for discretionary expenditures due to the fact that the measure does not deduct payments required for debt service and other items. Annual averages of non-GAAP measures represent the total value of the non-GAAP measure divided by the number of years during the forecast period.

We believe the projected non-GAAP financial measures included in this Annual Report on Form 10-K provide additional meaningful comparisons between the Company’s economic analysis and its peer companies. These projected non-GAAP financial measures are not historical measures of financial performance and are not presented in accordance with U.S. GAAP. They may exclude items that will be significant in understanding and assessing our financial results. Therefore, these measures should not be considered in isolation or as an alternative or superior to GAAP measures. You should be aware that our presentation of these measures have no standardized meaning under U.S GAAP and may not be comparable to similarly-titled measures used by other companies.

As the Project is not in production, the prospective non-GAAP financial measures are based on the estimated revenues, costs and other metrics set forth in the TRS, and are subject to the assumptions, qualifications and exceptions set forth in the TRS. The economic model included in the TRS is not a true cash flow model as defined by financial accounting standards but rather a representation of Project economics at a level of detail appropriate for a pre-feasibility study level of engineering and design. As such, the projected non-GAAP measures included in this Annual Report cannot be reconciled to comparable U.S. GAAP measures without unreasonable effort.