By Charles Pitts
Vertex Minerals’ approval to operate its Reward gold mine underground for almost the full day has turned a permitting change into an operating-cost test. The varied Environment Protection Licence issued by the NSW Environment Protection Authority allows continuous underground mining and blasting at any hour, increasing available underground working time from about nine hours to roughly 22 hours a day.
The processing plant remains a daytime operation, running from 6 a.m. to 6 p.m. That distinction matters. Vertex is not doubling plant capacity overnight; it is seeking to place more development metres, stope ore and mucking activity into the mine’s fixed-cost infrastructure before the daytime processing window begins.
At the same time, the company is moving toward narrower development profiles and mechanised longhole stoping. Together, those changes could influence three measures that usually determine whether a narrow-vein gold mine creates value: tonnes moved per shift, dilution and the number of economic mining fronts available over time.
Reward’s operating constraint has shifted
Under the former operating regime, blasting was restricted to a daytime window. If a heading was not charged and cleared before the cutoff, the mining cycle could roll forward by a full day. Ventilation clearance and re-entry also consumed productive shift time.
The varied licence allows underground mining, transport, rehabilitation and related activities around the clock. Blasting is permitted at any hour, subject to vibration, airblast and other environmental limits. Processing, construction and audible maintenance remain subject to separate operating windows.
Vertex says the change raises available underground working time from approximately nine hours per day to about 22 hours. That is not equivalent to 22 hours of continuous blasting. It is a measure of the time available to complete the broader mining cycle:
- Bogging and mucking
- Ground support
- Face drilling
- Charging and firing
- Ventilation clearance
- Re-entry and advance
The commercial logic is straightforward. The fleet, ventilation, dewatering systems and processing infrastructure represent a largely fixed cost base. More completed cycles can spread those costs over additional tonnes, provided development and stoping productivity improve as planned.
The first test is development productivity
Development is the leading indicator for a small underground mine because each completed metre can open access to additional stoping positions. It also determines how quickly an operation can build a reliable ore inventory ahead of the plant.
Vertex reported 38 metres of development advance and nine metres of rehabilitation during August. The company expects the longer working window to increase development metres by allowing firing, ventilation and re-entry to be scheduled around shift changes rather than concentrated inside a narrow daytime period.
The relevant question is not simply whether the mine can work longer. It is whether the additional hours translate into completed cycles per heading and more available production faces.
Industry comparisons show the range of outcomes possible from mechanised narrow-vein operations:
| Operating metric | Comparable benchmark or reported case | Relevance to Reward |
|---|---|---|
| Vertex August development advance | 38m, plus 9m rehabilitation | Current operating baseline |
| Mechanised narrow-vein jumbo development | About 180–240m per month per jumbo | Longer-term productivity reference |
| Total operating development in a multi-heading case | About 400–450m per month | Requires multiple active headings and support capacity |
| Mechanised narrow-vein stoping | About 6,500–7,500 tonnes per month | Broad benchmark, not a Reward forecast |
| Kafang mechanised stope capacity | Increased from 100t/day to 400t/day | Illustrates mining-method impact |
| Kafang stope cycle | Reduced from 390 days to 120 days | Shows the value of cycle-time control |
| Reward narrower development profile | 2.5m | Designed to reduce overbreak and dilution |
| Reward expected dilution reduction | More than 20% for equivalent cut length | Company target, not yet a reconciled result |
The benchmarks are not directly comparable with Reward. They may involve larger mines, different rock conditions, wider orebodies and more established fleets. Their value is as a framework for judging whether the licence change is producing measurable operating improvement.
A useful performance dashboard would therefore track advance per heading, metres per jumbo shift, drilling utilisation, re-entry time, tonnes bogged per hour and the number of active stoping fronts. Without those measures, “22-hour operations” remains an availability claim rather than a demonstrated productivity gain.
Dilution may matter more than the extra hours
Reward is working in narrow gold structures where the difference between ore and waste can be measured in tens of centimetres. Vertex expects new 2.5-metre development profiles to cut dilution by more than 20% for an equivalent cut length.
That target is important because the company’s initial longhole trial experienced some brow dilution associated with wider four-metre drives. The reported trial stopes were mined at widths of approximately 1.0 to 1.4 metres, with stope heights of about 8 to 9 metres.
Reducing the drive profile should bring the excavation closer to the geometry of the mineralised structure. In theory, that means less waste entering the ore stream, a higher delivered grade and less material competing for limited daytime processing capacity.
The trade-off is that narrower profiles can constrain equipment access, ventilation, ground support and turning radii. The operating result will depend on whether the smaller profile preserves drilling accuracy and cycle speed.
Research published through the AusIMM’s underground mining proceedings notes that narrow-vein mines must balance recovery, dilution, safety, capital cost and operating cost. Longhole open stoping is generally better suited to steeper and wider veins, while narrower structures may require more selective methods.
Vertex’s approach is to combine low-profile access with mechanised longhole stoping. That is a more demanding technical proposition than simply increasing equipment hours, but it could improve tonnes per worker while preserving selectivity.
August production shows why feed quality is critical
Vertex reported August processing of 1,262 tonnes at 1.62 grams per tonne gold and 64% recovery. The company reported 94 ounces produced, 49 ounces sold and 81 ounces available for sale.
Those figures represent a ramp-up phase rather than a mature production profile. Vertex has also said current feed contains diluted material and that gravity recovery improves at higher feed grades. That makes the development-profile change operationally important: dilution control has the potential to affect both head grade and recovery performance.
The daytime plant window creates another constraint. Underground production can continue during the night, but the mine must build and manage stockpiles so that the 6 a.m. to 6 p.m. plant operation receives consistent feed. A larger underground mining window therefore shifts part of the challenge from extraction to ore handling, stockpile management and plant scheduling.
Norseman shows the value of extending the mining front
Pantoro’s Racetrack discovery at the Norseman Gold Project illustrates the exploration side of the same operating equation. The company has extended the mineralised strike to about 900 metres, with results including:
- 11.12 metres at 5.48 grams per tonne gold from 488.6 metres
- 2.0 metres at 24.11 grams per tonne from 237 metres
- 1.29 metres at 51.46 grams per tonne from 498 metres
Mineralisation remains open to the east and down-dip. Pantoro is using three diamond rigs and an RC rig as it advances the discovery toward a maiden Mineral Resource estimate.
The company’s Norseman project information describes the broader operation as an established high-grade goldfield with existing underground infrastructure. That infrastructure matters because a new discovery located close to an operating mine can potentially be evaluated with lower incremental development requirements than a standalone deposit.
Racetrack is not yet a resource or reserve. The key milestones are still geological continuity, drilling confidence, mining access, geotechnical performance and a mine plan that can convert mineralisation into economic stopes.
For operators, the lesson is similar to Reward: mine life is extended not only by finding more ounces, but by creating additional productive fronts that can be accessed, drilled, blasted and extracted at an acceptable dilution level.
Automation can turn availability into utilisation
Longer operating windows also increase the value of automation and remote operation. Vertex has referred to remote-controlled loaders, Muki boom arrangements fitted to jumbo equipment and a dedicated Resemin Muki longhole rig for narrow underground conditions.
The immediate opportunity is not necessarily fully autonomous mining. It is better equipment utilisation and more consistent execution across the mining cycle.
Relevant technologies include:
- Remote-controlled loading and mucking in active or recently blasted areas
- Digital drill navigation and hole-deviation monitoring
- Automated ring design for longhole stopes
- Three-dimensional cavity and stope reconciliation
- Fleet tracking tied to shift, heading and cycle-time data
- Remote supervision from a control room
Sandvik’s AutoMine Aura and underground automation developments show how 3D perception and remote operation are being applied to underground equipment. For narrow-vein gold mines, the most immediate benefit may be safer and more consistent operation in areas where equipment access, ventilation or ground conditions limit direct exposure.
Automation cannot correct poor stope design or weak geological control. It can, however, reduce idle time, improve repeatability and provide the operating data needed to identify where additional hours are actually being lost.
Reward operating scenarios
The following framework is designed to test operating performance rather than predict a share price. It should be updated as Vertex reports reconciled development, stoping, grade and cost data.
| Scenario | Operating outcome | Main assumptions | Key risks |
|---|---|---|---|
| Bear | More available hours, but limited increase in saleable ounces | Development bottlenecks persist; dilution remains elevated; plant feed stays inconsistent | Ground conditions, equipment reliability, ventilation and recovery |
| Base | Higher development rates, improved stope availability and gradual reduction in unit costs | 22-hour underground availability converts into more completed cycles; 2.5m profiles reduce dilution; daytime plant runs consistently | Ramp-up delays and weaker-than-expected grade reconciliation |
| Bull | Sustained mine-rate increase with stronger grades and longer economic mine life | Mechanised longhole stoping performs at design widths; remote mucking improves utilisation; dilution falls by more than 20% | Geological continuity, longhole drilling accuracy and plant capacity |
The base case requires more than a regulatory approval. It requires a chain of evidence: higher metres per month, shorter cycle times, lower operational dilution, improved delivered grade and a stable plant feed profile.
What decision-makers should monitor next
The most useful indicators over the next operating periods are likely to be:
- Development metres per month and per jumbo shift
- Stope tonnes mined versus planned tonnes
- Operational dilution by stope and mining method
- Longhole drilling accuracy and overbreak at the brow
- Grade delivered to the ROM pad and plant recovery
- Night-shift equipment utilisation
- Cost per development metre and cost per tonne
- New stoping fronts opened through additional development
Reward’s 22-hour underground schedule is therefore best viewed as an operating experiment with regulatory permission behind it. If the added availability produces more advance, lower dilution and steadier feed to the daytime plant, the result could be a lower-cost and longer-lived gold operation.
If those links fail to materialise, the mine will simply have more permitted hours without a proportional increase in productive output. For narrow-vein gold, the decisive measure remains the same: how many payable ounces can be delivered from each metre developed, each stope fired and each tonne processed.
