Sunday Creek Gold-Antimony Project Exploration Decline Contract Awarded 2026

Why Underground Access Is the Real Catalyst at Sunday Creek

The history of large-scale mineral discovery is punctuated by inflection points, moments when a project transitions from a promising surface anomaly into something geologically definable and economically credible. Those moments rarely arrive through incremental drilling. They tend to arrive when a company fundamentally changes how it accesses the ground beneath it.

That principle sits at the heart of the decision by Southern Cross Gold Consolidated Ltd. to commission an underground exploration decline at its Sunday Creek gold-antimony project in Victoria, Australia. The awarding of the Sunday Creek gold-antimony project exploration decline contract to PYBAR Mining Services Ltd. in May 2026 is not simply a construction milestone. It represents the clearest signal yet that Sunday Creek is advancing beyond its surface exploration phase into a category of project that demands industrial-scale underground infrastructure.

Understanding what that shift means, and why it matters for both the project's geological definition timeline and its strategic positioning as a dual-commodity critical minerals asset, requires examining the mechanics of underground drilling, the nature of epizonal gold-antimony deposits, and the broader supply chain context in which antimony now sits.

The Physics of Underground Drilling and Why It Changes Everything

Surface drilling is a powerful and cost-effective tool in the early stages of exploration. It allows geologists to test large areas rapidly, establish grade continuity, and build preliminary geological models. However, surface drilling carries inherent constraints that become increasingly problematic as a deposit grows deeper and more geometrically complex.

Drill holes placed from surface must travel significant vertical distances before reaching the target zone. Over those distances, deviation accumulates, angle options narrow, and hole length requirements grow substantially. The result is that deep mineralisation is sampled obliquely, from angles that may not intersect the geometry of steeply dipping vein systems in the most informative way possible.

Underground drilling platforms solve these problems by repositioning the rig physically closer to the target. From a platform located 115 metres beneath surface, a drill crew can fire holes at angles that surface rigs simply cannot replicate. Hole lengths are shorter, completion times faster, and the resulting intercepts more precisely positioned relative to the geological structure being tested.

At Sunday Creek, this transition is designed to produce a step change in data density and geological understanding, not a marginal improvement on existing methodologies. Furthermore, interpreting drill results from underground platforms yields qualitatively richer three-dimensional data than surface programs alone can deliver.

From 11 Rigs to 24: The Scale of the Drilling Acceleration

As of May 2026, the Sunday Creek program was operating 11 surface rigs across the project area. The exploration decline, once commissioned, will enable the project to run up to 24 rigs simultaneously, combining both surface and underground platforms. That represents a 118% increase in active drilling capacity deployed in parallel across the system.

The primary decline will span approximately 680 metres in length, with a cross-section of 5.5 metres wide by 6 metres high and a vertical depth of roughly 115 metres. From that depth, approximately 1,200 metres of lateral development will create multiple independent drilling platforms, each capable of hosting dedicated diamond drilling setups targeting different parts of the mineralised system.

Michael Hudson, President and Chief Executive Officer of Southern Cross Gold, characterised the decline project in explicitly operational terms, noting that underground platforms 115 metres beneath surface would scale the program from the 11 surface rigs currently operating to 24 rigs working concurrently from underground positions, and that this positions Sunday Creek among the largest pre-development drill-outs globally. (Engineering & Mining Journal, May 5, 2026)

The box cut, which provides the surface entry point for the decline, has been developed to approximately 15 metres in depth. The overall construction contract was awarded to PYBAR Mining Services Ltd., a subsidiary of Thiess, following a competitive tender process evaluated across four criteria: technical capability, safety record, delivery schedule, and contract pricing. The contract term is approximately seven months, with targeted completion by year-end 2026.

What Makes Sunday Creek Geologically Distinctive

The Sunday Creek project is situated approximately 60 kilometres north of Melbourne, placing it within one of Australia's most infrastructure-accessible mining jurisdictions. The deposit is classified as an epizonal orogenic gold system, a deposit type defined by its relatively shallow depth of formation within the Earth's crust.

Epizonal deposits differ from their mesozonal and hypozonal counterparts in several important ways:

• They form at shallower crustal levels, typically under lower pressure and temperature conditions than deeper orogenic systems
• They tend to be hosted within structurally controlled quartz vein networks, often associated with regional fault corridors
• In Victoria specifically, epizonal systems frequently carry elevated concentrations of antimony alongside gold, a geochemical signature that reflects the particular fluid chemistry operative during mineralisation

Sunday Creek exhibits this antimony association clearly, and it is this characteristic that elevates the project beyond a conventional high-grade gold discovery into a dual-commodity asset with strategic industrial significance. In addition, the antimony critical mineral uses across defence, energy, and electronics manufacturing further amplify this project's strategic relevance.

The project's exploration target, as of March 2025, is summarised below. Readers should note that this represents a conceptual exploration target rather than a JORC-compliant Mineral Resource estimate. Sufficient geological data to support formal resource classification had not yet been established at the time of reporting.

By January 2026, the exploration program had completed 235 drill holes totalling 107,415 metres across five active prospect areas designated as Christina, Apollo, Leviathan, Tonstal, and Consols. The breadth of mineralised expression across multiple prospects suggests a structurally complex system with genuine potential for continuity at depth and along strike.

The JORC Pathway: Why Rig Count Matters to Investors

For investors tracking pre-development mineral exploration projects, the transition from conceptual exploration target to formal JORC Mineral Resource estimate is among the most significant re-rating events a company can deliver. It shifts the conversation from geological potential to geological fact, enabling more rigorous economic analysis, bankable feasibility work, and institutional investor engagement.

The challenge is that reaching JORC classification requires a density of drill hole data sufficient to demonstrate grade and tonnage continuity to the standards required by the Australian code. That data density takes time to generate, and time is directly proportional to rig count and drilling efficiency. Consequently, understanding the distinction between true width vs apparent width in reported intercepts becomes particularly important as the program scales.

Doubling the number of active rigs from 11 to 24 does not simply halve the time to resource definition in a linear sense. Underground drilling platforms generate cross-cutting intercepts that surface programs cannot produce, providing three-dimensional geological information that accelerates the modelling process disproportionately. The geometric information yielded by angled underground holes intersecting the same vein system from multiple directions is qualitatively different from what surface-only programs can deliver.

The critical insight here is that geological data from underground platforms is not just more abundant, it is structurally superior for building the three-dimensional models that underpin JORC Mineral Resource estimates.

Antimony's Strategic Position in the Global Critical Minerals Landscape

Antimony sits at an unusual intersection of industrial chemistry, defence manufacturing, and energy technology. Its applications span flame retardant formulations used throughout construction and electronics, lead-acid battery alloys, military-grade ammunition, and emerging grid-scale energy storage applications. This breadth of end-use markets, combined with a heavily geographically concentrated production base, has driven multiple Western governments, including Australia, the United States, and the European Union, to formally classify antimony as a critical mineral.

The significance of that classification for Sunday Creek lies in the structural demand dynamics it creates. Projects capable of supplying antimony from politically stable, infrastructure-rich jurisdictions are increasingly viewed through a supply chain security lens rather than purely as commodity plays. Furthermore, antimony supply risks in 2025 and beyond have sharpened the focus of Allied-nation governments on identifying reliable domestic and friendly-nation sources.

That changes the nature of potential offtake discussions, the profile of interested counterparties, and the broader strategic narrative available to the project's management team. Southern Cross Gold has framed Sunday Creek's long-term potential in terms of becoming a significant Allied-nation supplier of both gold and antimony, language that reflects the project's dual-commodity positioning but should be understood as a strategic aspiration at this stage of development rather than a confirmed commercial outcome.

The project remains in the pre-resource exploration phase, and any supply chain contribution remains subject to the successful completion of resource definition, feasibility studies, and project financing. For instance, progress toward a definitive feasibility study would represent a critical future milestone in validating the project's economic credentials.

Disclaimer: Forward-looking statements regarding antimony supply positioning represent management's stated objectives and not guaranteed outcomes. Investors should assess these projections in the context of the exploration-stage status of the project.

Government Approvals and the Regulatory Pathway Secured

Resources Victoria, the Victorian Government's mining regulatory division, granted formal Work Plan approval on November 27, 2025, authorising commencement of underground exploration decline development at Sunday Creek. This approval followed a structured assessment process covering environmental management, community consultation, and operational safety planning.

Premier Jacinta Allan publicly endorsed the project as a critical minerals jobs opportunity for Victoria, a statement that reflects the political attention being paid to domestic critical minerals development but should not be interpreted as project-specific government funding, backing, or accelerated permitting beyond the standard regulatory framework.

In the five months between the November 2025 Work Plan approval and the May 2026 PYBAR contract announcement, the company completed several foundational preparatory activities:

• Surface infrastructure establishment across the project site
• Procurement of secondary consents required before underground mining could commence
• Box cut ground support preparation and geotechnical establishment
• Portal establishment works to create the surface entry point for the decline

This sequential preparatory phase reflects standard practice for underground mining project commencement and demonstrates that the company had systematically addressed the pre-construction requirements before formalising the decline contract.

Building the Team for Underground Development

Infrastructure contracts and drilling programs require operational leadership to deliver on schedule and to specification. In parallel with the PYBAR contract award, Southern Cross Gold appointed two senior operational leaders to support the project's transition from surface exploration to underground development:

• Shane Leary was appointed as Projects Manager (Operations), a role focused on the overall management and delivery of the physical construction and development program
• Ben Edwards was appointed as Underground Development Manager, with specific responsibility for the underground development phase now underway

These appointments reflect an organisational transformation from an exploration-focused structure, characterised by geological and technical staff, toward a project development management model that requires construction management, safety systems, contractor coordination, and operational planning expertise.

The simultaneous management of an 11-rig surface drilling program, a major underground construction contract, and a newly expanded operational team represents significant organisational complexity. The parallel execution model, where exploration drilling, underground construction, and team build-out proceed simultaneously, is characteristic of projects where management has concluded that conventional sequential development would introduce unacceptable delays in the race to resource definition.

Land Position and Infrastructure Foundations

A frequently overlooked element of project development timelines is the question of land tenure and surface rights. Underground mining requires not only the subsurface mineral rights granted through exploration and mining licences but also the surface land rights necessary to establish portals, surface infrastructure, waste management facilities, and eventually processing plants.

Southern Cross Gold's acquisition of 1,054.5 hectares of freehold land surrounding the Sunday Creek project area in December 2024 directly addresses this constraint. Freehold ownership removes the negotiation complexity and tenure risk associated with surface access arrangements over third-party land and simplifies the approvals pathway for subsequent development stages.

Key Project Metrics at a Glance

Frequently Asked Questions: Understanding the Sunday Creek Exploration Decline

What is an exploration decline and how does it differ from a production decline?

An exploration decline is an underground tunnel driven at a downward gradient to provide physical access to mineralised zones beneath the surface. Unlike a production decline, which is constructed to extract ore at commercial scale with all the associated infrastructure for haulage, ventilation, and services, an exploration decline is designed primarily to position drilling equipment underground. Its purpose is data collection and geological definition, not ore production.

Why does underground drilling produce better geological data than surface drilling for deep deposits?

Underground platforms allow rigs to be positioned much closer to the target mineralisation, reducing hole lengths and therefore reducing the accumulation of drill hole deviation over distance. More importantly, underground platforms allow drill holes to be fired at angles that surface rigs cannot replicate, generating intercepts that cut across vein structures from multiple directions. This three-dimensional intersection pattern is essential for building the geological models that underpin JORC Mineral Resource estimates.

What is an epizonal orogenic gold deposit?

Epizonal deposits represent the shallowest formation depth category within the orogenic gold deposit classification system. They form within the upper portions of the Earth's crust under relatively lower temperature and pressure conditions than mesozonal or hypozonal systems. Victorian epizonal deposits are geologically notable for their propensity to carry elevated antimony concentrations alongside gold, a feature that reflects the specific hydrothermal fluid chemistry responsible for their formation.

When will the Sunday Creek exploration decline be completed?

Based on the seven-month contract term awarded to PYBAR Mining Services, the primary decline and associated lateral development are targeted for completion by the end of 2026.

What does the conceptual exploration target represent?

The conceptual exploration target of 2.2 to 3.2 million ounces AuEq at grades of 8.3 to 10.6 g/t represents a range of geological potential estimated from the available data at the time of reporting in March 2025. It is explicitly not a JORC-compliant Mineral Resource estimate and should not be interpreted as one. Sufficient geological data to support formal resource classification had not been established at that time. The target is a tool for guiding exploration strategy, not a statement of confirmed mineral inventory.

This article contains forward-looking statements, conceptual exploration targets, and strategic assessments that involve assumptions and uncertainties. These do not constitute investment advice. The Sunday Creek project is at an exploration stage of development and involves material risks. Past exploration results do not guarantee future resource definition outcomes. Readers should conduct their own due diligence and consult qualified financial advisors before making investment decisions.

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