Capricorn Metals has expanded its Orion South Underground Mineral Resource Estimate at Mt Gibson to 895,000 ounces, marking a 31% increase since July 2025. This growth, driven by extensive diamond drilling, underscores the project's underground potential alongside ongoing open pit operations.
- Orion South Underground resource increased to 895,000 ounces gold
- 31% growth since maiden underground resource in July 2025
- 33% of resource now classified as Indicated
- Resource remains open at depth and along strike
- Further drilling planned at Lexington and Hornet targets
Significant Resource Growth at Mt Gibson
Capricorn Metals has announced a substantial update to its underground gold resource at the Mt Gibson Gold Project (MGGP) in Western Australia. The Orion South Underground Mineral Resource Estimate (MRE) has grown to 9.5 million tonnes grading 2.9 grams per tonne gold, equating to 895,000 ounces. This represents a 31% increase, or an additional 211,000 ounces, since the maiden underground resource was reported just four months ago in July 2025.
The increase is the result of over 13,000 metres of focused underground diamond drilling, which has not only expanded the resource but also improved confidence levels, with 33% of the resource now classified as Indicated. This classification upgrade is critical as it supports the advancement towards a Pre-Feasibility Study and the estimation of a maiden Ore Reserve for the underground component.
Resource Open at Depth and Along Strike
The updated resource extends 220 metres below the deepest part of the current open pit design and covers only a 1.2-kilometre strike length of the more than 8-kilometre MGGP strike. Importantly, the mineralisation remains open at depth and along strike, suggesting further growth potential. The middle 100 vertical metres immediately below the pit design show a compelling grade density of 5,400 ounces per vertical metre, highlighting the high-grade nature of the deposit in this zone.
Capricorn is actively pursuing extensional drilling at Orion South and plans to commence drilling at other promising underground targets, including Lexington and Hornet, which could further enhance the project’s resource base.
Strategic Implications and Next Steps
Executive Chairman Mark Clark emphasised the company’s commitment to developing Mt Gibson into a long-life mining operation combining both open pit and underground mining methods. The updated underground resource forms the basis for a Mining Conceptual Study, which is an early assessment of the potential for underground mining at MGGP.
Ongoing infill drilling aims to convert more of the Inferred resource to Indicated, improving the robustness of the resource estimate. Concurrent technical studies, including geotechnical and hydrogeological assessments, are underway to support the estimation of a maiden underground Ore Reserve. Additionally, trade-off studies are being conducted to optimise the interface between underground and open pit mining, which is expected to modify the base of the current pit design for operational efficiency.
Environmental and Operational Considerations
The resource update assumes traditional long hole open stoping underground mining methods, common for steeply dipping ore bodies. Historical production and test work indicate that high gold recoveries are achievable using standard carbon-in-leach processing. Environmental planning includes progressive rehabilitation of waste rock dumps and tailings storage facilities designed to utilize mine waste for dam construction and water recovery.
With a solid foundation of drilling data and resource classification, Capricorn Metals is well positioned to advance Mt Gibson’s underground development, potentially extending the mine life and enhancing project economics.
Bottom Line?
Capricorn Metals’ underground resource surge at Mt Gibson signals a promising new chapter, but the path to a maiden Ore Reserve and production remains a critical next step.
Questions in the middle?
- How quickly can Capricorn convert the remaining Inferred resources to Indicated and Measured categories?
- What will be the economic impact of integrating underground mining with the existing open pit operations?
- How will ongoing drilling at Lexington and Hornet influence the overall resource and reserve profile?