First Phosphate Corp (CSE: PHOS) (OTCQX: FRSPF) (OTCQX ADR: FPHOY) (FSE: KD0)  is pleased to announce the results of its updated Mineral Resource Estimate for its Bégin-Lamarche project in Saguenay-Lac-Saint-Jean, Québec, Canada. The updated MRE includes results from the 2025-2026 drilling program described in the Company’s press release dated April 27, 2026.

• The updated MRE includes a 378% increase in Indicated Mineral Resources over the Company’s Initial MRE dated September 9, 2024.

• Measured pit-constrained Mineral Resource: 6.2 Mt @ 7.70% P₂O₅ (phosphate).

• Indicated pit-constrained Mineral Resource: 198.5 Mt @ 6.00% P₂O₅.

• Inferred pit-constrained Mineral Resource: 89.5 Mt @ 6.16% P₂O₅.

• The Deposit remains open at depth.

• Metallurgical test work indicates an anticipated apatite concentrate grade of 40.4% P₂O₅ at an 88% process recovery rate, with very low levels of potentially deleterious elements, and has been qualified for production of battery-grade phosphoric acid for lithium iron phosphate battery with a conversion ratio of 91.1%.

• The Deposit is located next to existing road and hydroelectric infrastructure and at only 70 km driving distance from the deep-sea Port of Saguenay.

• The Deposit benefits from definitive, long-term, partially prepaid offtake from an existing, creditworthy partner.

• Apatite (phosphorus, phosphate) is listed on the critical minerals lists of Québec, Canada, the United States and the European Union.

“We are pleased with the results of our 2025-2026 drilling exploration program and the quantity and quality upgrade provided to our Mineral Resources,” says First Phosphate CEO, John Passalacqua. “We are now able to continue to move the project forward with great confidence in our Mineral Resources.”

The updated MRE, with an effective date of May 1, 2026, was carried out by Mr. Antoine Yassa, P.Geo., of P&E Mining Consultants Inc., who is an Independent Qualified Person within the meaning of Canadian Securities Administrators’ National Instrument 43-101: Standards of Disclosure for Mineral Projects.

The Bégin-Lamarche Phosphate Deposit contains a significant phosphate Mineral Resource that is associated with well-defined oxide-apatite peridotite intrusions within the large Lac-Saint-Jean anorthosite suite. The LSJAS is the largest phosphate-mineralized anorthosite worldwide. The phosphate Deposit is comprised of four mineralized zones which are continuous, only separated by faults within the Deposit and extend over a length of 2,750 m (Figure 1). The Mountain Zone is a single phosphate-bearing mass having a diameter of up to 200 m and a length of 250 m. The Northern zone is comprised of four phosphate layers ranging from 30 m to 200 m in thickness and a length of 625 m. The Central Zone bears eight phosphate layers, one of them having up to 50 m in thickness and extending to 900 m. The Southern Zone bears three phosphate layers, one of them having up to 125 m in thickness and extending to 725 m.

Figure 1 – The Bégin-Lamarche Deposit Updated Optimized Pit Shell

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The Bégin-Lamarche Deposit mineralized wireframes boundaries were determined from lithology, structure, and grade boundary interpretation based on visual inspection of drill hole cross-sections. Four mineralized wireframe zones were developed and referred to as the Mountain, Northern, Central and Southern Zones. The mineralized wireframes were constructed on 50 m spaced vertical cross-sections, with on-screen digitized polylines on drill hole cross-sections in GEMS™. The mineralized wireframe outlines were influenced by the selection of mineralized material above 2.5% P₂O₅ that demonstrated a lithological and structural zonal continuity along strike and down dip. In some cases, mineralization <2.5% P₂O₅ was included for the purpose of maintaining mineralized zone continuity. The minimum constrained width for mineralized wireframe interpretation was 3 m of drill core length.

The Bégin-Lamarche Mineral Resource Estimate is based on 276 drill holes totalling 68,345 m. The database contained 20,682 analyses for percentage of P₂O₅. The Mineral Resource Estimate is presented in Table 1.

Note: P₂O₅ = phosphorus pentoxide.

1. Mineral Resources, which are not Mineral Reserves, do not have demonstrated economic viability.

2. The estimate of Mineral Resources may be materially affected by environmental, permitting, legal, title, taxation, socio-political, marketing, or other relevant issues.

3. The Inferred Mineral Resource in this estimate has a lower level of confidence than that applied to an Indicated Mineral Resource and must not be converted to a Mineral Reserve. The Company expects that the majority of the Inferred Mineral Resource may be upgraded to an Indicated Mineral Resource with continued exploration.

4. The Mineral Resources in this press release were estimated using the Canadian Institute of Mining, Metallurgy and Petroleum, CIM Standards on Mineral Resources and Reserves, Definitions (2014) and Best Practices Guidelines (2019) prepared by the CIM Standing Committee on Reserve Definitions and adopted by the CIM Council.

The Bégin-Lamarche Mineral Resource Estimate was derived from applying a 2.5% P₂O₅ cut-off value to the pit-constrained block model and reporting the resulting tonnes and grades for potentially mineable areas. The following parameters were used to calculate the cut-off value that determines the open pit potentially economic portion of the constrained mineralization (Table 2).

The P₂O₅ cut-off value is calculated with parameters below:

• US$:C$ Exchange Rate: $0.72
• P₂O₅ Price (32%): US$225/t (approx five-year trailing average)
• P₂O₅ Price (40%): US$280/t
• P₂O₅ Process Recovery: 88%
• Processing & Conc Transport Cost: C$20/t
• G&A: $1.50/t
• Mining Cost: C$2.75/t (mineralized material and waste)
• Pit Slopes: 45^°

Accordingly, the P₂O₅ cut-off of potential open pit mining is calculated to be = 2.5%.

The optimized pit-constrained Mineral Resource Estimate is moderately sensitive to the selection of reporting P₂O₅cut-off values, as demonstrated in Table 2.

Metallurgical Testwork has been successfully conducted by SGS at their Québec City facility with additional support by SGS Lakefield Ontario. Recent test results have confirmed that an apatite concentrate can be obtained analyzing 40.4% P₂O₅ and at 88% recovery.

First Phosphate’s Bégin-Lamarche Deposit is located approximately 50 km driving distance north of the City of Saguenay, Québec’s sixth-largest city, which hosts daily flights to Montréal, a skilled industrial workforce, strong local infrastructure, and which is 30 km driving distance from the deep-sea Port of Saguenay.

The geological and drilling work was planned, carried out and supervised by Laurentia Exploration Inc. The drill core was logged at Lamarche near the Deposit and at Laurentia Exploration’s offices. The drill core was sawed and sampled at Laurentia Exploration’s offices in Jonquière.

Qualified Persons

The scientific and technical disclosure for First Phosphate included in this News Release have been reviewed and approved by Steeve Lavoie, P.Geo. Mr. Lavoie is Chief Geologist of the Company and a Qualified Person under National Instrument 43-101 Standards of Disclosure of Mineral Projects.

The Qualified Person independent of the issuer, responsible for estimating the Mineral Resources of the Begin-Lamarche Property, within the meaning of NI 43-101, is Mr. Antoine Yassa, P.Geo., of the firm P&E Mining Consultants Inc. Mr. Yassa has read and approved the scientific and technical information in this press release for accuracy and compliance with NI 43-101.

P&E Mining Consultants Inc., an associate group of 20 geological and mine engineering professionals established in 2004, provides geological and mine engineering consulting reports, Mineral Resource and Mineral Reserve Estimates, NI 43-101 Technical Reports, Preliminary Economic Assessments, Pre-Feasibility and Feasibility Studies.

Laurentia Exploration inc. is a firm of consulting geologists based in Jonquière, Saguenay Lac-St-Jean. It has 80 employees, mainly geology professionals who are members in good standing of a professional order. The firm was founded in 2017 and carries out projects throughout Québec and Ontario.

About First Phosphate Corp.

First Phosphate (CSE: PHOS) (OTCQX: FRSPF) (OTCQX ADR: FPHOY) (FSE: KD0) is a mineral exploration and development and clean technology company dedicated to building and reshoring a vertically integrated mine-to-market supply chain for the production of LFP batteries in North America. Target markets include energy storage, data centers, robotics, mobility, and national security.

First Phosphate’s flagship Bégin-Lamarche property, located in Saguenay-Lac-Saint-Jean, Québec, Canada, represents a rare North American igneous phosphate resource producing high-purity phosphate characterized by very low levels of impurities.

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