Capricorn’s high-grade Mt Gibson hits: underground design notes for mine engineers
Reviewed by Joe Ashwell

First reported on Australian Mining
30 Second Briefing
Capricorn Metals has reported further high-grade gold intercepts at the Mt Gibson gold project in Western Australia, including 6m at 57.38g/t from 616m depth and 7m at 40.01g/t from 401m at the Lexington prospect. The mineralisation occurs beneath the planned open pit and is being tested with deep diamond drilling targeting down-plunge extensions. Results strengthen the case for an underground resource, with implications for redesigning mine schedules, ventilation and ground support around narrow but very high-grade stopes.
Technical Brief
- Narrow, very high-grade lodes will likely require tight drill spacing for robust underground resource classification.
- Any underground redesign will need to integrate with existing Mt Gibson pit geotechnical domains and wall stability assumptions.
- Ventilation and escape-way layouts must account for deep, localised stopes directly under active or planned pits.
- Ground support schemes will need to manage stress concentrations around slender stopes at depth.
- Mine scheduling could shift to a combined open-pit/underground sequence, affecting haulage, backfill timing and dewatering.
Our Take
Capricorn Metals’ recent record output at the Karlawinda gold project in Western Australia, alongside the completion of its throughput expansion, suggests Mt Gibson is being advanced into a portfolio that already has a proven large-scale processing hub in the same state, which could de-risk future development options.
The acquisition of the Extension Hill and Mungada ground from Mount Gibson Iron in the Mid West, referenced in earlier coverage, indicates that the Mt Gibson gold project is part of a broader land-position build-out in this corridor rather than a standalone play, giving Capricorn more flexibility in how it sequences drilling and potential mine development.
With our database showing hundreds of gold-tagged mining pieces but only a handful reporting such high grades at depths beyond 400–600m in Western Australia, the Lexington prospect intercepts point towards an underground-style target that could complement Capricorn’s predominantly open-pit production base.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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