Perseus Mining’s Yaouré Underground Project Expands West African Gold Frontier

Perseus Mining's Yaouré Underground Project: Expanding West Africa's Gold Frontier

The Yaouré Gold Mine in Côte d'Ivoire stands at a pivotal moment in its development history with Perseus Mining's strategic underground expansion. This landmark project represents not only a significant evolution for Perseus's flagship operation but also marks a historic milestone as Côte d'Ivoire's first underground gold mine. With a US$170 million investment commitment, the company aims to extend Yaouré's productive life well into the next decade while maintaining its position as the lowest-cost asset in Perseus's West African portfolio.

The Strategic Significance of Yaouré Underground

The Yaouré operation has rapidly established itself as Perseus Mining's crown jewel since achieving commercial production in 2021. The mine delivered 262,000 ounces in FY25 at an all-in sustaining cost (AISC) of US$1,101 per ounce, making it the company's most efficient producer. The underground development aims to capitalize on this operational excellence by accessing deeper high-grade resources beneath the existing open pit.

Perseus Mining's overall production profile is well-balanced with Yaouré contributing over half of the company's annual gold output. The group produced 496,551 ounces in FY25 at an AISC of US$1,235 per ounce, demonstrating strong operational performance across their West African portfolio.

Presidential Approval and Development Timeline

In September 2025, Perseus Mining secured a critical milestone when Côte d'Ivoire's President Alassane Ouattara signed the presidential decree authorizing the CMA underground project. This approval followed the Environmental and Social Impact Assessment clearance received in May 2025, completing the regulatory framework needed to advance the project.

The development timeline includes:

• January 2025: Underground mining contract awarded to Byrnecut
• September 2025: Presidential decree authorization received
• January 2026: First ore expected from underground development
• March 2027: Commercial production targeted to commence

This fast-tracked approval process demonstrates the strong relationship Perseus has cultivated with Ivorian authorities and their recognition of the project's economic importance for the country's developing mining sector.

What Makes the Yaouré Underground Project Technically Distinctive?

Geological Framework and Mineralization Patterns

The Yaouré gold deposit is situated within the Paleoproterozoic Birimian greenstone belt, characterized by a complex geological setting that includes mafic volcanic rocks, granodiorite intrusions, and volcaniclastic sequences. The mineralization primarily occurs along north-south trending structures controlled by brittle-ductile shear zones.

The CMA underground project targets the down-dip extension of the CMA open pit, where mineralization continues at depth with consistent grade profiles. The mineralized package includes:

• A 20-meter-thick zone containing visible gold in the CMA sequence
• Multiple higher-grade lenses within steeply dipping quartz veins
• Potential for additional parallel structures as exploration continues

Geologists familiar with West African gold deposits note that the Yaouré mineralization system demonstrates remarkable continuity at depth, unlike some other deposits in the region that become more structurally complex with increasing depth.

Resource Base and Reserve Definition

The underground development has significantly enhanced Yaouré's resource profile, with current drilling interpretation details extending to 185 meters below the pit floor for reserves and 350 meters for inferred resources. The updated resource statement shows:

The CMA underground area specifically contains over 966,000 ounces in measured and indicated resources and approximately 514,000 ounces in inferred resources, providing substantial inventory for future mining.

What's particularly notable is the slightly higher grade profile in the inferred resources (1.9 g/t) compared to the measured and indicated resources (1.59 g/t), suggesting potential grade improvement at depth—a pattern observed in several Birimian belt deposits.

Mining Approach and Infrastructure Development

The underground mining method will utilize conventional decline access with mechanized development and production. Byrnecut, an experienced international underground contractor with operations across Africa, Australia, and North America, will implement a four-year mining plan focusing on:

• Development of a main decline from a portal near the existing pit
• Establishment of level access drives at regular vertical intervals
• Implementation of longhole open stoping with paste backfill
• Integration with existing processing infrastructure

The 3.3 million tonne per annum processing plant will continue to handle both open pit and underground ore, with the underground contribution gradually increasing as development progresses. This shared infrastructure approach significantly reduces capital intensity compared to standalone underground operations.

How Will Yaouré Underground Impact Perseus Mining's Production Profile?

Production Forecasts and Mine Life Extension

The Yaouré underground project extends the mine's operational life to at least 2035, significantly beyond the original open pit plan. This extension provides Perseus with production visibility for over a decade, supporting the company's target of maintaining annual gold production around 530,000 ounces.

Key production metrics include:

• Continued processing capacity of 3.3 million tonnes per annum
• Gradual integration of higher-grade underground ore into the mill feed
• Potential for production optimization as underground operations mature
• Exploration upside from ongoing resource definition drilling

Mining analysts note this extension transforms Perseus from a mid-term producer into a long-life gold company, addressing a key investor concern about mine life sustainability in the mid-tier gold sector.

Financial Impact and Investment Returns

Perseus Mining's strong financial position, with US$827 million in cash and bullion at FY25 year-end and zero debt, enables the company to fund the US$170 million underground development without external financing. The investment decision reflects the project's compelling economics, with expected returns including:

• Maintenance of Yaouré's position as the lowest-cost operation in the portfolio
• Potential for improved blended head grades as higher-grade underground ore is introduced
• Enhanced cash flow generation in a strong gold price environment
• Capital efficiency through utilization of existing surface infrastructure

With record high gold prices exceeding US$4,000 per ounce in October 2025, the project's economics look particularly robust, potentially delivering accelerated payback periods compared to initial feasibility studies conducted at lower gold price assumptions.

Operational Synergies and Cost Structure

The integration of underground operations with the existing open pit creates significant operational synergies, including:

• Shared processing facilities and infrastructure
• Common management and technical services teams
• Optimized workforce utilization and training opportunities
• Streamlined regulatory compliance and community engagement

These synergies help maintain Yaouré's competitive cost structure, with the underground operation expected to deliver ore at costs comparable to or better than the current open pit on a per-ounce basis when considering the higher underground grades.

Underground mining experts point out that the ability to develop from an operating site rather than a greenfield location provides substantial advantages in terms of site knowledge, geological understanding, and operational readiness.

What Environmental and Social Considerations Shape the Project?

Sustainability Framework and Environmental Management

Perseus Mining has developed a comprehensive sustainability framework for the Yaouré underground expansion, building on its established environmental management systems. Key elements include:

• Water management strategies for underground dewatering
• Energy efficiency initiatives to minimize carbon footprint
• Waste rock characterization and management planning
• Progressive rehabilitation of disturbed areas

The company's environmental performance at Yaouré has been strong, with zero significant environmental incidents reported in FY25 and emissions intensity maintained at approximately 0.56 tonnes of CO₂ equivalent per ounce produced.

Environmental engineers familiar with West African mining note that underground operations typically have smaller surface footprints than open pits, potentially reducing overall impact as the operation transitions to predominantly underground mining.

Community Engagement and Local Development

The Yaouré operation has established deep roots in the local community, with Perseus investing US$5.63 million in community development initiatives across its Côte d'Ivoire operations in FY25. The underground project will further enhance local benefits through:

• Additional employment opportunities for local residents
• Skills development programs focused on underground mining techniques
• Expanded local procurement, building on the US$545 million spent with local suppliers in FY25
• Infrastructure improvements benefiting surrounding communities

Perseus maintains a workforce that is 94% comprised of national employees, with ongoing efforts to increase the representation of women in leadership roles beyond the current 6%.

The company's focus on local capacity building has created a pipeline of skilled Ivorian professionals who will form the core of the underground workforce, potentially establishing expertise that could be deployed at future underground developments in the country.

Safety Performance and Workforce Development

Safety remains paramount as Perseus transitions to underground operations, building on the company's strong safety record that saw a 43% reduction in Total Recordable Injury Frequency Rate to 0.6 in FY25. Specific initiatives for the underground development include:

• Comprehensive training programs for underground-specific hazards
• Enhanced ground control management systems
• Regular emergency response drills and capability development
• Continuous improvement through leading indicator monitoring

Safety specialists point out that the transition from open pit to underground mining represents a significant cultural and technical shift requiring specialized training and safety systems. Perseus's partnership with Byrnecut, which maintains industry-leading safety programs, positions the company well for this transition.

How Does Yaouré Underground Compare to Regional Peers?

Competitive Positioning in West African Gold Sector

The Yaouré underground project strengthens Perseus Mining's position among West African gold producers, with several distinctive advantages:

• First-mover status as developer of Côte d'Ivoire's inaugural underground gold mine
• Integration with an existing high-performance open pit operation
• Strong government relationships demonstrated by presidential-level project approval
• Balanced country risk profile across operations in Ghana and Côte d'Ivoire

Compared to regional peers developing standalone underground projects, Yaouré benefits from established infrastructure, an experienced workforce, and existing regulatory frameworks.

Mining investment analysts note that the project's 2035 mine life horizon places Perseus in the top quartile of West African gold producers for production visibility, addressing a key investor concern about reserve replacement in the region.

Technical Innovation and Best Practices

Perseus is implementing several technical innovations at Yaouré underground that set new standards for the region:

• Advanced ground control monitoring systems
• Automated equipment for development and production
• Digital twin modeling for optimized mine planning
• Ventilation on demand systems to reduce energy consumption

These mining innovation trends not only improve operational efficiency but also enhance safety and environmental performance, establishing benchmarks for future underground developments in West Africa.

Mining technology specialists highlight that these investments in next-generation mining systems position Yaouré to be among the most technologically advanced underground gold mines in Africa, potentially delivering productivity advantages over conventional operations.

What Future Growth Opportunities Exist Beyond the Current Plan?

Exploration Potential and Resource Growth

Significant exploration upside remains at Yaouré, with the CMA structure open at depth and along strike. Ongoing mineral exploration insights aim to:

• Convert inferred resources to indicated category
• Test extensions beyond the current 350-meter depth limit
• Explore parallel structures identified through geophysical surveys
• Evaluate satellite deposits within the broader mining lease

The company's exploration strategy focuses on near-mine opportunities that could leverage existing infrastructure, potentially extending mine life beyond the current 2035 horizon.

Exploration geologists familiar with the Birimian belt note that many major gold systems in the region demonstrate mineralization continuing to depths of 600-1,000 meters, suggesting considerable potential beyond the current 350-meter exploration depth at Yaouré.

Processing Optimization and Recovery Enhancements

Perseus continues to evaluate opportunities to optimize the Yaouré processing plant as underground ore contribution increases. Potential initiatives include:

• Grinding circuit modifications to handle harder underground ore
• Recovery enhancement through improved gravity circuit performance
• Reagent optimization for different ore types
• Throughput balancing between open pit and underground sources

These technical improvements could further enhance the project's economics and operational flexibility.

Metallurgists point out that underground ore typically exhibits different physical and chemical characteristics than open pit material, often with lower oxidation levels and different liberation characteristics. Optimizing the plant for these differences represents an opportunity for recovery and throughput improvements.

What Are the Key Milestones to Monitor?

Investors and stakeholders should track several critical milestones as the Yaouré underground project advances:

1. Development Progress (Q4 2025 – Q1 2026)

   • Portal establishment and initial decline development
   • Underground infrastructure installation
   • Equipment commissioning and workforce mobilization

2. Production Ramp-up (Q1 2026 – Q1 2027)

   • First ore delivery to processing plant
   • Grade reconciliation against resource model
   • Development rates and productivity metrics

3. Commercial Production (Q2 2027 onwards)

   • Achievement of nameplate capacity
   • Cost performance against budget
   • Integration with open pit operations

4. Exploration Results

   • Resource expansion drilling outcomes
   • Conversion of inferred to indicated resources
   • Discovery of new mineralized zones

Project management specialists emphasize that the first 6-12 months of underground development typically establish the foundation for long-term project success, with early performance indicators providing insights into execution quality and geological model accuracy.

Strategic Significance for Perseus Mining

The Yaouré underground project represents a pivotal evolution in Perseus Mining's growth strategy, transforming its flagship operation from a medium-term open pit mine into a long-life gold asset with production visibility well into the next decade. With strong financial backing, technical expertise, and government support, the project positions Perseus to maintain its production profile of approximately 500,000 ounces annually at competitive costs.

As gold prices remain robust above US$4,000 per ounce in late 2025, the timing of this development provides Perseus with enhanced leverage to the strong commodity price environment while maintaining the financial discipline that has characterized its debt-free balance sheet and consistent shareholder returns.

The historic nature of Côte d'Ivoire's first underground gold mine further cements Perseus's position as a technical leader in West African mining, potentially opening doors to additional opportunities in the region as governments seek experienced operators for complex projects.

The company's financial strength, with US$827 million in cash and bullion and zero debt, provides significant flexibility for both project execution and potential additional growth initiatives, distinguishing Perseus from many peers that operate with constrained balance sheets or limited financial flexibility.

Frequently Asked Questions

When will the Yaouré underground mine begin producing gold?

First ore from the underground development is expected in January 2026, with commercial production targeted to commence in March 2027.

How much is Perseus investing in the underground expansion?

Perseus Mining has committed US$170 million to develop the Yaouré underground project, funded entirely from existing cash reserves.

How long will the Yaouré mine operate with the underground expansion?

The underground development extends Yaouré's mine life to at least 2035, with potential for further extensions through ongoing exploration and evolving mine reclamation practices.

Who is constructing the underground mine?

Byrnecut, an international underground mining contractor with extensive African experience, was awarded the four-year mining contract in January 2025.

What makes this project significant for Côte d'Ivoire?

The Yaouré underground development will be Côte d'Ivoire's first underground gold mine, representing a milestone in the country's mining sector development and technical capabilities.

How does the underground project affect Perseus's production profile?

The underground expansion helps maintain Perseus's annual gold production target of approximately 530,000 ounces by extending Yaouré's productive life.

What is the current resource base for the underground project?

The CMA underground area contains over 966,000 ounces in measured and indicated resources and approximately 514,000 ounces in inferred resources.

How does Perseus plan to fund the development?

Perseus will fund the US$170 million investment from its existing cash reserves, which stood at US$827 million at the end of FY25, maintaining its debt-free status.

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