SFR.V · 2025-12-16 12:00:00

Sandfire Resources America Announces Results of Updated Pre-Feasibility Study for the Johnny Lee Deposit and Updated Mineral Resource for the Lowry Deposit at the Black Butte Copper Project Updated PFS for the Johnny Lee Deposit and new Mineral Resource estimate for the nearby

Resource Estimates Economic Studies

17 E Main Street

PO Box 431

White Sulphur Springs, MT 59645

Tel: (406) 547-3466

Fax: (406) 547-3719

Web: www.sandfireamerica.com

Email: [email protected]

Sandfire Resources America Announces Results of Updated

Pre-Feasibility Study for the Johnny Lee Deposit and Updated

Mineral Resource for the Lowry Deposit at the Black Butte

Copper Project

Updated PFS for the Johnny Lee Deposit and new Mineral Resource estimate for the nearby

Lowry Deposit underline the high-grade underground copper potential, with a Probable

Mineral Reserve for the Johnny Lee Deposit of 9.5Mt at 2.9% Cu for 270,000t of copper and

an 8-year life at the Black Butte Copper Project in Montana, USA, that aligns with the

stringent Mine Operating Permit conditions.

White Sulphur Springs, Montana – December 16, 2025 – Sandfire Resources America Inc.

(“Sandfire America” or the “Company”) is pleased to announce its updated Mineral Resource and

Reserve and the results of the Preliminary Feasibility Study Update (the “Study Update” or “PFS”)

for the Johnny Lee deposit at its Black Butte Copper Project in White Sulphur Springs, Montana,

USA, pursuant to National Instrument 43-101 – Standards of Disclosure for Mineral Projects (“NI

43-101”).

The Study Update relates to Mineral Resources and Reserves associated with the Johnny Lee copper

deposit, the cornerstone deposit at the Black Butte Copper Project (the " Johnny Lee Deposit" or

the “Project”).

The Company is also pleased to announce an updated Mineral Resource for the Lowry copper deposit

(the "Lowry Deposit"), which is located approximately 3km south-east of the Johnny Lee Deposit.

Study Update Highlights:

• Average annual post-tax cashflows of US$78 million per annum for the first five years

of operations.

• The Project is forecast to generate US$2.3 billion in gross revenue and US$1.0 billion in

pre-tax net cashflow during mine operations, based on a copper price of US$4.70/lb.

• Updated Measured and Indicated Mineral Resource of 18.9 million tonnes at 2.4% copper

for 462,000 tonnes of contained copper and Inferred Mineral Resource of 3.4 million

tonnes at 1.9% copper for 64,000 tonnes of contained copper completed for the Johnny Lee

Deposit.

• Using a Net Smelter Return cut off value of US$110/t, the Probable Mineral Reserves have

increased from 8.8Mt at 2.6% Cu for 230,000 tonnes of contained copper in 2020 to 9.5

million tonnes at 2.9% copper for 270,000 tonnes of contained copper for the 2025 PFS,

defined for the Johnny Lee Upper and Lower Copper Zones.

• The Project has been designed in accordance with all standards and obligations

required under the Project’s stringent Mine Operating Permit conditions.

• The Johnny Lee Deposit underpins an 8-year mine life and is designed to be mined at 1.2

million tonnes of ore per annum, with the processing plant producing ~35,000 tonnes per

annum of contained copper in the initial four years of operation.

• Forecast production totaling 1,039,000 dry metric tonnes of copper concentrate containing

234,000 tonnes of copper metal over the life of the mine.

• Average annual production of ~29,000 tonnes of copper metal over an initial 8 year

mine life at a direct operating cash cost (C1) of US$2.56/lb.

• The Project has a pre-tax NPV8% of US$143 million (IRR=13.6%) and a post-tax NPV8% of

US$99 million (IRR=11.3%).

• With a 10% movement in copper price, which is close to the current spot price for copper,

pre-tax NPV 8% increases to US$288 million (IRR=19.4%) with a post -tax NPV 8% of

US$217 million (IRR=16.0%).

Construction capital cost of US$474 million.

• For the Lowry Deposit, located 3km south-east of the Johnny Lee Deposit, a Measured and

Indicated Resource of 6.6 million tonnes at 2.4% copper for 154,000 of contained copper,

and Inferred Mineral Resource of 2.8 million tonnes at 2.1% copper for 58,000 tonnes

of contained copper has been defined for the 2025 PFS as compared to solely an inferred

resource outlined in 2020:

o The updated Mineral Resource is based on updated geological modeling, resource

estimation, classification, and mineralogy/recovery assumptions.

o The Lowry Deposit is not covered by the current environmental permits and will

need to undergo further permitting and approvals process.

• The Study Update economic analysis is based on the Johnny Lee Deposit Mineral Reserves

and does not include the Lowry Deposit.

Commenting on the Study Update completion and key outcomes, Sandfire America CEO Lincoln

Greenidge stated:

“Today’s results mark an important milestone for the Black Butte Copper Project and reaffirm our

confidence in the world- class potential of the Johnny Lee and Lowry deposits. The updated PFS

confirms Johnny Lee ’s highest-grade potential of any known undeveloped underground copper

deposit in the United States, and it does so while meeting, and in many cases exceeding, the rigorous

environmental and operational standards set out in our Mine Operating Permit. This reinforces our

longstanding commitment to responsible, modern mining in Montana.

Importantly, the new Mineral Resource estimate for the Lowry Deposit underscores the scale of the

broader area and highlights a powerful opportunity for future growth beyond the initial 8-year mine

plan. Together, these updates position Black Butte as a st rategically significant domestic copper

project at a time when U.S. supply of critical minerals has never been more essential.

Our focus now turns to advancing the project through completion of a feasibility study. We remain

committed to the development of a modern, environmentally responsible operation that will deliver

long-term economic benefits to Meagher County and to the State of Montana, while creating

meaningful value for our shareholders.”

1. Black Butte Copper Project Overview

The Black Butte Copper Project consists of 7,684 hectares of fee simple lands held under mineral

lease by the Company and 1,040 unpatented mining claims on U.S. Forest Service Lands (USFS),

leased by the Company, totaling 8,078 hectares. The Black Butte Copper Project is located in south-

central Montana in Meagher County, 27 km north of White Sulphur Springs.

Johnny Lee Deposit

The Johnny Lee Deposit was discovered by a joint venture between Cominco American Inc. and

Utah International in 1985. The Johnny Lee Deposit is comprised of two zones of mineralization: an

upper copper zone (“JL UCZ”) situated at depths of 40m – 210m below surface and an underlying

lower copper zone (“JL LCZ”) at depths of 340m – 520m below surface.

A mine operating plan (“MOP”) application for the extraction of mineralized rock from both zones

of the Johnny Lee Deposit was submitted to the Montana Department of Environmental Quality

(“MT DEQ”) in December 2015. The application was deemed to be complete and compliant, and a

draft MOP permit was issued by the MT DEQ on September 18, 2017. After a full Environmental

Impact Statement (“EIS”) process, a MT DEQ positive record of decision was received on April 9,

2020, allowing for the development and underground mining of the Johnny Lee Deposit to proceed.

On August 14, 2020, the MT DEQ approved the bond posting and issued a Final Mine Operating

Permit allowing the Company the right to commence Phase I Development surface construction at

the mine site.

Following a 2020 legal challenge to the Mine Operating Permit, on February 26, 2024, the Company

received a positive ruling by the Montana Supreme Court reversing a 2021 district court decision and

instructed the district judge to have the MT DEQ completely reinstate Tintina Montana Inc.’s Mine

Operating Permit of the Black Butte Copper Project. The Montana Supreme Court granted the

Company’s request for summary judgement allowing the Company to move forward with

construction of its highly engineered, underground copper mine. The Company won on all counts in

the Montana Supreme Court with a 5- 2 decision upholding the 2020 decision of the MT DEQ to

allow responsible copper mining at the Black Butte Copper Project.

The MOP proposes underground mining of the Johnny Lee Deposit using a drift and fill mining

method and production of a copper concentrate by milling and froth flotation. Mill tailings will be

used for underground paste-fill support and the surplus deposited in a double-lined cemented tailings

storage facility.

Lowry Deposit

The Lowry Deposit, a similar style copper deposit to the Johnny Lee Deposit, is located

approximately 3km to the south-east of the Johnny Lee Deposit. Copper mineralization is primarily

hosted in the Lowry Middle Copper Zone (“LMCZ”) and Lowry Lower Copper Zone (“LLCZ”),

surrounded by a lower grade “halo” of copper mineralization.

For further details about the Project, please go to the Sandfire Resources America Inc. website at

www.sandfireamerica.com.

2. Study Update (PFS)

The current study is an underground Pre- Feasibility Study for the Johnny Lee D eposit, building on

the prior Preliminary Economic Assessment (PEA, 2013) and the subsequent Feasibility Study

completed in 2020, which defined an initial Mineral Reserve for the Johnny Lee Deposit. The Study

Update incorporates updated geological and structural models for the JL UCZ and JL LCZ, revised

Mineral Resource and Mineral Reserve estimates, updated metallurgical test work and recovery

models, integrated with systematic mineralogy and geometallurgical modelling, and updated capital

and operating cost estimates and refining charges, using long- term copper price assumptions of

US$4.70/lb.

The Study Update mine plan and economic analysis are based only on the Johnny Lee Deposit

Mineral Reserves. The Lowry Deposit is covered by a separate Inferred Mineral Resource estimate

and is not included in the current mine plan, production schedule, or economic analysis. Development

of the Lowry Deposit would require additional technical studies, environmental review , and

permitting.

2.1 Economic Analysis

The Study Update economic analysis is based on the Johnny Lee Deposit Mineral Reserves. The

Study Update does NOT include the Lowry Deposit.

The copper price assumption adopted for the base case is US$4.70/lb. from the start of production.

The Project’s post-tax NPV at an 8% discount rate is estimated to be US$99M with an IRR of 11.3%.

Pre-tax NPV at an 8% discount rate is estimated to be US$143M with an IRR of 13.6%. Initial capital

costs are estimated to be US$474M, and sustaining capital is estimated to be US$82M. Cash Costs

(C1) are estimated to be US $2.56/lb. of copper. The life-of-mine all-in sustaining cost is estimated

to be US$2.83/lb. of copper. Payback of start -up capital is achieved approximately 4 years from

commissioning.

2.2 Johnny Lee Deposit - Mineral Reserves

The Mineral Reserve was prepared in accordance with Canadian Institute of Mining and Metallurgy

and Petroleum (“CIM”) Definition Standards and will be supported by the Study Update pursuant to

the NI 43 -101 “Standards for Disclosure for Mineral Project”, to be published and filed on the

Company’s website and SEDAR+ profile within 45 days.

A net smelter return (“NSR”) value was calculated for each block in a geological block model based

on metallurgical recovery, grade, price and payability factors. Mine design shapes were generated

based on an NSR cut-off value of US$110/t (operating cost). An NSR cut-off value of US$45/t

(incremental operating cost) was used to determine whether material should be sent to waste or

processed. Detailed mine designs were created with dilution and recovery factors applied, mineral

resource classification considered plus other modifying factors and economic viability tested. The

Mineral Reserve for the Johnny Lee Deposit is shown in Table 1.

Table 1 – Mineral Reserve Johnny Lee Deposit

Class Diluted Tonnes Cu Grade Contained Cu Metal

(t)

Proven - - -

Probable 9,500,000 2.9% 270,000

Total 9,500,000 2.9% 270,000

Notes:

1. The Qualified Person for the Mineral Reserve estimate is Shane McLeay FAusIMM.

2. Effective date: November 14, 2025. All Mineral Reserves have been estimated in accordance wit h

IM definitions, as required under NI 43-101.

3. Mineral Reserves were estimated using a US $4.70 /lb. Cu price and NSR cut-off value s of

US$110/

t (operating cost) and US$45/t (incremental operating cost).

4. Tonnages are rounded to the nearest 100 kt, metal grades are rounded to one decimal place, an d

etal tonnes are rounded the nearest 10kt. All units are metric.

5. Rounding as required by reporting guidelines may result in summation differences.

6. Average LOM Metallurgical Recovery is 95% for JL LCZ, 78% for JL UCZ, and 86% combined.

7. Mineral Reserves are based on the Mineral Resource estimate effective November 5, 2025.

8. Mineral Reserves are a subset of Mineral Resources.

The Mineral Reserves identified in Table 1 comply with CIM definitions and standards for a NI 43-

101 technical report. Detailed information on mining, processing, metallurgical, and other relevant

factors demonstrate, at the time of the Study Update, that economic extraction is feasible. The Study

Update did not identify any mining, metallurgical, infrastructure or other relevant factors that may

materially affect the estimates of the Mineral Reserves or potential production. Table 2 below shows

the Mineral Reserves broken out by zone.

Table 2 – Mineral Reserves for the Johnny Lee Deposit by Zone

Zone Class Diluted Tonnes Cu Grade Contained Cu Metal

(Tonnes)

JL UCZ Total

Proven - - -

Probable 6,700,000 2.2% 140,000

Total 6,700,000 2.2% 140,000

JL LCZ Total

Proven - - -

Probable 2,800,000 4.6% 130,000

Total 2,800,000 4.6% 130,000

Project Total Total 9,500,000 2.9% 270,000

Notes:

1. Tonnages are rounded to the nearest 100 kt, metal grades are rounded to one decimal place, and

metal tonnes are rounded the nearest 10kt. All units are metric.

2. Rounding as required by reporting guidelines may result in summation differences.

3. Mineral Reserves were estimated using a US $4.70 /lb. Cu price and NSR cut-off value s of

US$110/t (operating cost) and US$45/t (incremental operating cost).

2.3 Johnny Lee Deposit - Mineral Resource Estimate

The updated Mineral Resource estimate for the Johnny Lee D eposit has been prepared under the

supervision of Berkley Tracy, P. Geo (PGO#3024) of SRK Consulting (U.S.), Inc., an independent

Qualified Person (QP) under NI 43-101.

A total of 305 drillholes were used to inform the 2025 Johnny Lee Deposit geology model and

Mineral Resource estimate including historical and recent drilling between 2010 and present . The

Mineral Resource statement is supported by recent updates to the geological modeling, resource

estimation, and mineralogy with recovery assumptions in addition to historic drilling, analyses, and

studies. Mineralization is hosted in two distinct zones of > 1.2% Cu mineralization, JL UCZ and JL

LCZ.

Drillhole intersection spacing in the JL UCZ ranges from 10 – 100 m. The JL UCZ is hosted by

dolomitic shale with abundant massive pyrite beds and some dolomite layers.

Many of the drillholes that intersected the JL UCZ were stopped-short of the JL LCZ; consequently,

drillhole spacing in the JL LCZ is larger than that of the JL UCZ, ranging from 50 – 200m. The JL

LCZ occurs below the Volcano Valley fault . The JL LCZ is hosted by interbedded shale,

conglomerate, and pyrite beds at the base of the Newland Formation.

Variable metallurgical recoveries for the JL UCZ required modeling on a block-by-block basis. The

JL LCZ has an overall average of 95% recovery. Based on the new test work, the increased recovery

values were used in the current calculation of NSR. Mineral Resource classification was assigned to

the Johnny Lee Deposit block model by the QP based upon: geological knowledge, continuity of Cu

grade within mineralized zones, thickness of the mineralized zones, confidence in the underlying

data (logging, assay, and physical testing), spatial continuity as determined through variography for

Cu, recovery data, and kriging quality variables (kriging efficiency, slope or regression, average

distance to samples, and estimation run pass). Blocks within the JL UCZ and JL LCZ have been

categorized consistent with NI 43 -101 and the CIM definitions and guidelines. A combination of

block scripting and manual smoothing with polylines was used to apply the appropriate block

classification of Mineral Resource categories.

Mineral Resources for the Johnny Lee Deposit have been calculated and reported using an economic

cut-off value (CoV), as estimated in the resource block model. The Mineral Resource statements are

supported by drilling, analyses, geological modelling, and metallurgical studies that determined

updated recoveries. The deposits have been classified into Measured, Indicated, and Inferred Mineral

resources, as per CIM definitions and are summarized in Table 3.

Table 3 – Johnny Lee Deposit Mineral Resource at US$45.00/t NSR, effective November 5, 2025 –

SRK Consulting (U.S.), Inc.

Mineral Resource