Boab Metals has increased the Sorby Hills mineral resource by 7% to 50.6Mt, while contained silver rises by 1.6Moz. More Measured and Indicated material now supports the mine plan, although the update does not yet change Ore Reserves, production targets or project economics.
- 50.6Mt resource at 3.0% lead, 34g/t silver and 0.4% zinc
- Contained silver increases to 54.66Moz
- Measured and Indicated resources rise 10% across Bimota, Omega and Norton
- New NSR domains add lower-grade lead and higher-grade silver mineralisation
- Phase IX assays remain outside the current estimate
Boab Metals Limited (ASX:BML) has added 1.6 million ounces of contained silver to the Sorby Hills resource, lifting the Western Australian project’s total Mineral Resource Estimate to 50.6 million tonnes. The updated inventory grades 3.0% lead, 34 grams per tonne silver and 0.4% zinc, representing a 7% increase in tonnage against the previous 2021 estimate.
Higher-confidence tonnes at the mine-plan deposits
The most consequential change is not simply the larger headline tonnage. Infill drilling lifted Measured and Indicated resources by 10% across Bimota, Omega and Norton, the three deposits identified as underpinning the baseload feed for Sorby Hills. Across the global resource, Measured and Indicated material now totals 25.8Mt, compared with 23.6Mt in the previously reported estimate.
Those deposits account for the bulk of the updated inventory: Bimota contains 3.2Mt, Omega 18.4Mt and Norton 22.8Mt. Norton remains the largest by tonnage, but much of its resource is Inferred, with 17.1Mt in that category. The classification matters because the company says the increased confidence in the early production feed is intended to support the planned mining schedule, while Inferred material carries a lower level of geological confidence.
Silver-rich NSR domains broaden the estimate
ERM International Group’s update used a net smelter return-based approach to identify mineralisation that a lead-focused model had previously left out. The new domains are predominantly lower-grade lead material, generally below 1% lead, associated with silver grades above 10g/t. Twenty-three such domains were modelled across Bimota, Omega and Norton, contributing 1.7Mt and 874,000 ounces of silver to the reported estimate.
The change also removes the 1% tonnage reduction factor previously applied for interpreted porosity at those three deposits. The Competent Person concluded that updated information, modelling and density work placed the remaining uncertainty within an acceptable estimation tolerance. That makes the comparison with 2021 less clean than the headline 7% increase suggests: the factor has been removed for Bimota, Omega and Norton, but remains in place for the unchanged Aprilia, Alpha and Beta estimates.
Phase IX drilling remains outside the resource
Boab has not yet incorporated results from its 47-hole Phase IX drilling programme. The announcement highlights an Omega intersection of 12.6 metres at 121g/t silver and 7.65% lead from 23 metres, but reports the interval as downhole length rather than confirmed true width. Its exclusion leaves a defined catalyst for a future resource update, but the current estimate should be assessed on its own reported data rather than on prospective additions.
Nor does the new MRE itself alter the Ore Reserve, mine plan, production target or project economics. Boab says those implications require separate assessment. The resource is therefore a stronger geological foundation for Sorby Hills, but the next test is whether the higher-confidence tonnes and newly modelled silver-bearing zones translate into mineable reserves and a revised delivery plan without weakening the project’s operating assumptions.
Bottom Line?
The resource has improved in both scale and confidence, but the investment case still turns on the separate conversion of that inventory into Ore Reserves and a mine schedule. Phase IX assays could add to the story, but they are not part of today’s numbers.
Questions in the middle?
- How much of the additional Measured and Indicated material will convert into Ore Reserves?
- Will Phase IX assays expand the mine plan, extend mine life or simply refine existing resource boundaries?
- How will the removal of the tonnage reduction factor affect future reserve estimates and project economics?