STLLR Gold Delivers Updated Mineral Resource Estimate and PEA Demonstrating US$1.0 Billion After-Tax NPV5% for the Large-Scale Tower Gold Project in Ontario, Canada

2025-05-15

TSX - Toronto Stock Exchange · Silver · Gold · Copper · Molybdenum · Canada

Average annual gold production of 273,000 ounces for 19-years, including peak average annual production of 316,000 ounces over the first five years, and a maximum annual production of 325,000 ounces in Year 15.

5.2 million ounces of gold production over the 19 years of conceptual mine life ("CML").

Base Case After-Tax NPV5%of C$1.36 billion (US$1.01 billion) and IRR of 13.4% at US$2,500/oz gold.

Spot Price After-Tax NPV5%of C$3.30 billion (US$2.46 billion) and IRR of 24.0% at US$3,200/oz gold.

2025 MRE (as defined herein): 4.0 million ounces from 140.4 Mt grading 0.89 g/t Au in the Indicated category and 7.0 million ounces from 200.3 Mt grading 1.08 g/t Au in the Inferred category.

2025 PEA (as defined herein) is preliminary in nature and includes inferred mineral resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves, and there is no certainty that the 2025 PEA will be realized. Mineral resources that are not mineral reserves do not have demonstrated economic viability.

Toronto, Ontario--(Newsfile Corp. - May 15, 2025) - STLLR Gold Inc.(TSX: STLR) (OTCQX: STLRF) (FSE: O9D) ("STLLR" or the "Company") announces the summary results of the updated Mineral Resource Estimate ("2025 MRE") and updated Preliminary Economic Assessment ("2025 PEA") for its 100%-owned Tower Gold Project ("Tower" or the "Project") located in the prolific Timmins Mining Camp in Ontario, Canada. The 2025 MRE was prepared by InnovExplo (a member of Norda Stelo) and the 2025 PEA was compiled by G Mining Services ("GMS").

Table 1: 2025 PEA1Economics _

| Potential Economics | Gold Price Assumption | | | US$2,500/oz Base Case | US$3,200/oz Spot | | | Pre-tax internal rate of return ("IRR")(%) | 16.1% | 28.6% | | After-tax IRR | 13.4% | 24.0% | | Pre-tax net present value at 5% discount rate ("NPV5%")(C$M) | C$2,118 | C$4,961 | | After-tax NPV5%(C$M) | C$1,355 | C$3,298 | | CML after-tax free cash flow ("FCF")(C$M)2 | C$3,438 | C$6,739 | | FX rate assumption (USD/CAD) | 1.34 | 1.34 | | After-tax NPV5%/Initial Capex ratio | 0.7x | 1.8x | | After-tax Payback period (years) | 5.8 | 2.9 |

_*Figures may vary slightly due to rounding_

Table 2: 2025 PEA1: Conceptual Mine Plan Summary _

_*Figures may vary slightly due to rounding_

STLLR President and CEO Keyvan Salehi, P.Eng. commented: "Tower is one of Canada's largest undeveloped gold projects, with size and scale matched only by a few Canadian gold projects. The 2025 PEA showcases the potential to produce 273,000 ounces of gold annually over 19 years, with peak production of 325,000 ounces. We believe the 2025 PEA delivers compelling economics with defensible capital and operating cost estimates. We designed the conceptual mine plan to maximize the output, which we believe is the best path to advance the Project and deliver long-term value. Furthermore, it is also our view that the geological environment hosting the Project continues along strike and at depth with solid upside potential for exploration. We believe this mine plan represents a strong foundation for a project with meaningful potential to grow in size, scale, and conceptual mine life."

"The 2025 MRE and 2025 PEA represent major advancements for Tower. We rebuilt the geological model from first principles, integrating detailed structural and lithological data to better represent the gold mineralization. Our disciplined approach has strengthened the 2025 MRE, increasing confidence and credibility, while laying the groundwork for more targeted and efficient future drilling. The Tower deposits remain open at depth and along strike to the west and east, with strong potential for expansion. In tandem, the mine plan was also developed using a comprehensive, bottom-up approach grounded in first principles, delivering a technically robust and executable strategy. Opportunities to grow the known mineralization, optimize the mine plan, and enhance project economics will continue to be pursued aggressively. Pre-Feasibility Study work is underway, with completion targeted for 2027. In parallel, we are advancing permitting efforts to potentially bring Tower to shovel-ready status by 2029. We believe Tower is one of a select group of large-scale gold projects in Ontario with a clear path to development in the foreseeable future."

Construction and Development Plan

Located 100 km east of Timmins, Ontario, along Highway 101, the Project benefits from proximity to existing regional infrastructure, including paved highways, power distribution, and local supply chains. Its proximity to Timmins, Kirkland Lake, and Matheson, provides access to a skilled and experienced labour pool.

The construction plan focuses initially on the development of the OP deposits, supported by the installation of key surface infrastructure, including a processing plant, tailings management facility ("TMF"), and other essential site services. The construction phase will be executed under an Integrated Project Management Team ("IPMT") model over a 30-month period. Pre-production activities will begin in month 24, with first gold production expected during the subsequent 6-month commissioning and ramp-up phase.

Stripping of overburden will commence at month 7, and OP mining operations will transition to a primarily owner-operated model upon the start of commercial production. Note that certain functions, such as explosives delivery to the hole, will remain under the responsibility of specialized contractors or suppliers.

During the construction period, approximately 58 Mt of OVB will be removed to access mineralized material, with an additional 230 Mt of OVB scheduled for removal over the CML. Upon completion of mill construction, approximately 1.4 Mt of OP mineralized material is expected to be processed during the commissioning period, yielding an estimated 43,181 ounces of pre-production gold.

UG development will begin after the 30-month construction phase and the commencement of commercial production. UG development will focus on lateral development, including the establishment of multiple ramp systems from surface, and the staged acquisition of mobile mining equipment. Over the CML, approximately 191,033 metres ("m") of lateral development is planned, providing access to 5 mining zones within the UG deposit.

Conceptual Mine Plan

The Project's 19-year conceptual mine plan contemplates the OP and UG mining of mineralized material from two primary areas: Golden Highway(western extent) and Garrison(eastern extent).

OP Mining: The OP mine plan is based on conventional drill, blast, load, and haul methods utilizing double benching of 10-metre benches. The Windjammer deposits (South, Central, and North), located within the Golden Highway Area, contain the majority of the OP mineralization. A total of seven (7) pits with up to three (3) phases each are planned over the CML to sequence mineralized material and manage strip ratios at Golden Highway and Garrison.

OP production is designed for a throughput of approximately 22,000 tpd, or 7.8 Mtpa, at an average head grade of 0.75 g/t Au. The average strip ratio is estimated at 4.3:1 (excluding OVB) and 6.3:1 (including OVB).

The 2025 MRE and 2025 PEA reflect increased estimates for waste rock and OVB relative to the 2022 PEA[7]. These changes are primarily attributable to:

MRE

A reconstructed geological model, developed from first principles, which integrates updated structural and lithological data for improved representation of mineralization geometry.

New geological data from the infill drilling programs has been incorporated in the latest domaining, which more confidently models the mineralized vein domains. This refinement has led to reduced mineralized material and increased classification of surrounding material as waste.

PEA

The adoption of an engineered first-principles pit design, inclusive of ramp placement and minimum mining width constraints, which has decreased overall slope angles and increased waste volumes.

Revised geotechnical parameters, resulting in shallower overburden slopes and, consequently, larger overburden volumes.

UG Mining: The UG mine plan employs a mechanized long-hole stoping method, accessed through multiple surface portals and ramp systems. Stopes will be mined in a bottom-up sequence, drilled and blasted, and then backfilled with either cemented rock fill or uncemented rockfill, depending on geotechnical and operational requirements.

Planned stope dimensions average 25.0 m (height) × 20.0 m (length) × 11.5 m (width), with an estimated average stope tonnage of 14,490 tonnes (inclusive of dilution and mining losses). UG operations are expected to contribute approximately 4,760 tpd (1.7 Mtpa) to the mine plan, supported by a consistent cycle of stopes in development, active mining, and backfill phases throughout the CML.

Potential Production: With a 92.7% mill recovery (see "Processing" section), the project is expected to produce 5.2 Moz of payable gold over the CML, averaging 273,000 ounces annually for 19 years (see Tables 2 and 3 and Figure 1 for more details on the conceptual mine plan)

Table 3: 2025 PEA - Conceptual Mine Plan*

| | OP | UG | Total | | | | | | | | | | | Material | Waste Rock | OVB | Grade Milled | Contained Gold | Material | Grade Milled | Contained Gold | Contained Gold | Recovery | Payable Gold | | Year | (Kt) | (Kt) | (Kt) | (g/t Au) | (Koz) | (Kt) | (g/t Au) | (Koz) | (Koz) | (%) | (Koz) | | -2 | | | 27,828 | | | | | | | | | | -1 | 1,437 | 12,060 | 30,060 | 1.08 | 50 | | | | 50 | 86.6% | 43 | | 1 | 9,225 | 32,184 | 28,117 | 1.05 | 312 | 1 | 1.89 | 0.08 | 312 | 91.5% | 285 | | 2 | 9,056 | 25,865 | 29,900 | 0.76 | 223 | 364 | 2.43 | 29 | 251 | 92.5% | 232 | | 3 | 8,016 | 31,925 | 30,005 | 0.91 | 233 | 1,480 | 2.43 | 115 | 349 | 88.9% | 310 | | 4 | 7,752 | 30,588 | 29,831 | 0.83 | 207 | 1,745 | 2.34 | 131 | 339 | 93.4% | 316 | | 5 | 7,770 | 46,683 | 12,535 | 0.64 | 160 | 1,739 | 2.00 | 112 | 271 | 92.9% | 252 | | 6 | 7,755 | 34,664 | 25,007 | 0.66 | 164 | 1,756 | 2.22 | 125 | 289 | 92.8% | 269 | | 7 | 7,741 | 59,511 | 2,748 | 0.78 | 193 | 1,732 | 2.16 | 120 | 314 | 92.8% | 291 | | 8 | 7,821 | 61,921 | 258 | 0.74 | 187 | 1,711 | 2.27 | 125 | 311 | 92.8% | 288 | | 9 | 7,647 | 61,842 | - | 0.65 | 161 | 1,641 | 2.29 | 121 | 281 | 92.9% | 262 | | 10 | 7,787 | 49,256 | - | 0.59 | 147 | 1,719 | 2.37 | 131 | 278 | 93.0% | 258 | | 11 | 7,680 | 37,168 | - | 0.65 | 161 | 1,767 | 2.30 | 131 | 291 | 92.6% | 270 | | 12 | 7,787 | 27,898 | 4,212 | 0.60 | 150 | 1,724 | 2.30 | 127 | 277 | 92.9% | 257 | | 13 | 7,791 | 19,156 | 16,673 | 0.65 | 163 | 1,700 | 2.59 | 142 | 305 | 93.4% | 285 | | 14 | 7,744 | 13,870 | 23,304 | 0.67 | 167 | 1,763 | 2.72 | 154 | 322 | 93.4% | 300 | | 15 | 7,739 | 30,128 | 6,743 | 0.86 | 213 | 1,722 | 2.46 | 136 | 349 | 93.1% | 325 | | 16 | 7,699 | 26,037 | 1,961 | 0.83 | 205 | 1,629 | 2.59 | 136 | 341 | 93.5% | 318 | | 17 | 7,657 | 15,970 | 15,345 | 0.72 | 178 | 1,562 | 2.34 | 118 | 296 | 92.9% | 275 | | 18 | 8,188 | 26,949 | 3,728 | 0.74 | 195 | 887 | 2.06 | 59 | 253 | 93.4% | 237 | | 19 | 5,922 | 8,993 | | 0.89 | 170 | | | | 170 | 95.0% | 161 | | Total | 150,211 | 652,667 | 288,254 | 0.75 | 3,638 | 26,643 | 2.35 | 2,011 | 5,649 | 92.70% | 5,234 |

_* Figures may vary slightly due to rounding _

Processing

The 2025 PEA contemplates processing mineralized material through a conventional milling, gravity concentration, and leaching circuit. The processing plant is planned to be located in the Golden Highway Area, strategically positioned near the center of gravity of the CML tonnage to optimize haulage efficiency across the project. The processing plant includes a primary crusher, semi-autogenous grinding ("SAG") mill including pebble crushing, gravity recovery circuit integrated with intensive leach reactor, two ball mills, followed by a Leach-CIP Carousel ("CIL") recovery process, Carbon desorption and regeneration, electrowinning circuit, gold room, and cyanide destruction.

The processing plant is designed to operate at up to 26,030 tpd, equivalent to approximately 9.5 Mtpa. Average gold recovery is estimated at 92.7%.

Other Site Infrastructure

The 2025 PEA includes the phased construction of a conventional TMF, located in the Garrison Area (near Buffonta) of Tower. The TMF is designed to accommodate all CML tailings generated by the processing facility. In addition to the processing plant and TMF, major site infrastructure will include:

A truck shop and supporting maintenance buildings

Site-wide haul roads

A high-voltage transmission line

A 400-person camp

An effluent water treatment plant

Surface water management ponds

Site admin buildings, mine dry, assay lab, as well as other pertinent infrastructure

This infrastructure layout has been optimized to support phased development and long-term operational efficiency. See Figure 2 for the proposed Tower site infrastructure layout.

Capex and Opex

Please refer to Tables 4 and 5 for the capex and opex summaries, respectively. Initial capex and sustaining capex assume the full upfront purchase of equipment without the use of lease financing.

Table 4 - Summary of the 2025 PEA Capex _

| Capex item | Initial (C$M) | Sustaining (C$M) | Total (C$M) | | Infrastructure | $123 | $12 | $135 | | Power & Electrical | $214 | | $214 | | Water Management, TMF & Earthworks | $135 | $108 | $243 | | Surface Operations | $29 | | $29 | | Open Pit Mining | $355 | $769 | $1,124 | | UG Mining | | $834 | $834 | | Processing (including the mill) | $265 | | $265 | | General Services (Owner's Costs) | $85 | | $85 | | Pre-Production, Start-Up, & Commissioning | $187 | | $187 | | | | | | | Total Directs: | $1,393 | $1,723 | $3,115 | | Total Indirects | $235 | | $235 | | Closure Cost & Monitoring Costs | | $77 | $77 | | Salvage Value | | ($44) | ($44) | | Contingency | $246 | | $246 | | Total Capex | $1,873 | $1,756 | $3,628 | | Less: Pre-Prod. Credit net of TC/RC & Royalties | ($144) | | ($144) | | Total Capex Net of Pre-Prod. | $1,729 | $1,756 | $3,485 |

_*Figures may vary slightly due to rounding _

_Table 5 - Summary of the 2025 PEA Opex*#_

| Opex Item | CML (C$M) | Unit (C$/t) | Unit (per oz) | | Total Mining (OP+UG) | C$5,935 | $33.84/t milled | C$1,143 (US$853) | | OP mining (less capex) | C$3,603 | $20.54/t milled | | | UG mining | C$2,333 | $13.30/t milled | | | Processing (incl. power) | C$2,086 | $11.89/t milled | C$402 (US$300) | | G&A | C$786 | $4.48/t milled | C$151 (US$113) | | Total operating cost | C$8,807 | $50.21/t milled | C$ 1,697 (US$1,266) | | Refining and transport | C$35 | | C$7 | | 1.5% royalties (Garrison) | C$59 | | C$11 | | Total Cash Costs5 | C$8,901 | C$50.74/t | C$1,715 (US$1,280) | | Total AISC6 | C$10,700 | - | C$2,059 (US$1,537) | | Total AIC6 | C$12,575 | - | C$2,403 (US$1,793) |

_* Figures may vary slightly due to rounding #AIC includes pre-production costs, tonnes, and ounces_

[](https://images.newsfilecorp.com/files/4852/252346_1d89f24db4ba7994_001full.jpg)

Figure 1: Annual Potential Production, Cost and FCF Profile To view an enhanced version of this graphic, please visit: https://images.newsfilecorp.com/files/4852/252346_1d89f24db4ba7994_001full.jpg

Taxes, Royalties, and Other Production Taxes

Corporate taxable income for operations in Ontario are subject to a combined (federal and provincial) income tax rate of 26.5%. Tower would qualify for the Ontario manufacturing and processing tax credit. Furthermore, the Ontario Mining Regulations require the payment of Ontario Mining Tax ("OMT") levied at a rate of 10.0% on taxable profits, in excess of C$500,000, which is incorporated into the financial model. OMT is deductible in calculating taxable income for corporate purposes. In the Garrison Area of Tower, the properties contain an average net smelter royalty ("NSR") of 1.5%.

Economics

Using a base case gold price of US$2,500 per ounce and a USD:CAD exchange rate of 1.34, the Tower Gold Project is estimated to generate an after-tax NPV5%of US$1.0 billion and an after-tax IRR of 13.4%. Sensitivity tables (see Table 8) have been prepared to illustrate the impact of key variables on project economics, including fluctuations in gold price, capital and operating costs, and discount rate.

Permitting

The 2025 PEA provides the basis for the project notice and project description that will kick off the Provincial and Federal permitting process for Tower, including the Federal Impact Assessment ("IA") and associated environmental studies. STLLR will continue to engage with local Indigenous communities and municipalities as we advance to the next stage of our Tower project.

Tower 2025 MRE8

The 2025 MRE incorporates over 516,770 m of drilling from 1,848 holes and was independently prepared by InnovExplo (a member of Norda Stelo Inc.) in accordance with National Instrument 43-101 - _Standards of Disclosure for Mineral Projects of the Canadian Securities Administrators_("NI 43-101") and follows current CIM Definition Standards (2014) and CIM MRMR Best Practice Guidelines (2019). For more details, see Tables 6 and 7 for the summary and breakdown by deposit, respectively.

The 2025 MRE is comprised of 9 deposits in two areas (see Figures 4 and 5 for OP and UG block model diagrams):

_Golden Highway Area:_55 Zone, Westaway, Southwest, Windjammer South, Windjammer Central, and Windjammer North9.

_Garrison Area:_903, Jonpol and, Garrcon.

The 2025 MRE has an effective date of May 2, 2025 and supports the 2025 PEA.

Table 6: 2025 MRE Summary8* (Effective date of May 2, 2025). Please review "Notes to Accompany the 2025 MRE" for additional information.

| Potential mining method | Indicated Mineral Resource | Inferred Mineral Resource | | | | | | Tonnes (Kt) | Grade (g/t Au) | Contained Gold (oz Au) | Tonnes (Kt) | Grade (g/t Au) | Contained Gold (oz Au) | | | OP | 135,230 | 0.84 | 3,656,400 | 157,837 | 0.81 | 4,133,600 | | UG | 5,194 | 2.07 | 345,800 | 42,456 | 2.07 | 2,827,100 | | Total (OP+UG) | 140,424 | 0.89 | 4,002,200 | 200,293 | 1.08 | 6,960,700 |

_*Numbers may not add up due to rounding_

There is no certainty that the 2025 MRE will be converted to Proven and Probable Mineral Reserve categories or will be realized in the future. Mineral Resource estimates that are not Mineral Reserves do not have demonstrated economic viability. The 2025 MRE may be materially affected by environmental, permitting, legal, title, taxation, socio-political, marketing, or other relevant risks, uncertainties and other factors, as more particularly described in the Cautionary Statements at the end of this news release.