Capricorn Metals has significantly upgraded the underground resource at its Mt Gibson Gold Project and released a positive conceptual study outlining the potential for a large-scale underground mine.
The Orion South Underground mineral resource estimate (MRE) has increased by 31 per cent, or 211,000 ounces, since July 2025, bringing the total to 9.5 million tonnes at 2.9 grams per tonne (g/t) Au for 895,000 ounces (oz) of gold. The rapid growth was based on over 13,000m of focused diamond drilling.
“We are now committed to a strategy of growing the underground resource, delivering ore reserves and incorporating these higher-grade underground zones into the mine plan,” Capricorn executive chairman Mark Clark said.
“This work will drive Capricorn towards validating our long-held belief that Mt Gibson will become a long mine life open pit and underground mining operation.”
Following the resource update, Capricorn completed an underground mining conceptual study based on the new 895,000oz MRE. The preliminary study, which was completed to an approximately 35 per cent level of accuracy, identified a conceptual mine plan containing 6.1 million tonnes (Mt) at 2.6g/t for 513,000oz of gold.
The proposed underground operation would use a pillared long-hole open stoping method, with access via two declines from the Aries pit. This setup could run concurrently with open-pit mining and is benchmarked as capable of a haulage rate of 1–1.2mt per annum.
Mark Clark said the study “has been successful in demonstrating an opportunity to potentially undertake underground mining” alongside open-pit operations.
While the study is conceptual and based on an MRE that is 67 per cent inferred, the positive results have prompted Capricorn to initiate a pre-feasibility study. Extensional drilling is underway, with the Orion South resource remaining strongly open at depth.
