Sibanye Posts 23% Cost Blowout at Century as Keliber Advances

Sibanye-Stillwater delivered two sharply different operational stories in H1 2026. In Finland, its Keliber lithium project advanced well beyond the construction phase, entering active commissioning with the concentrator plant brought online. In Australia, the Century zinc operation posted a 12% production decline and a 23% cost blowout driven by grade deterioration, weather, and maintenance shutdowns.

The contrast matters because the full H1 2026 interim results land on Tuesday, 1 September 2026. This is the last window to assess what the company’s two most visible diversification assets are actually telling investors before the complete financials arrive.

Here is what the Keliber milestone and the Century shortfall reveal about how Sibanye’s diversification strategy is performing in practice, not in the investor presentations, and what questions to bring to tomorrow’s full results.

Keliber reaches commissioning as Sibanye’s battery metals bet moves from paper to practice

Keliber’s progression from construction to commissioning during H1 2026 is the most tangible evidence yet that Sibanye-Stillwater’s battery metals ambitions are real and operational, not just strategic intent.

Open-pit extraction got underway at the Syväjärvi deposit in Finland, yielding approximately 217,500 tonnes of ore across the half. The concentrator facility moved into hot commissioning during the same period. Those are concrete milestones:

• Mining initiated at the Syväjärvi open pit, with approximately 217,500 tonnes of ore extracted
• Hot commissioning of the concentrator commenced during H1 2026
• Refinery start-up positioned as the next phase, contingent on prevailing lithium market conditions

The third point is where the story shifts from progress to uncertainty. Management has described the ramp-up as deliberately phased and cautious. The refinery is not on a fixed timeline; its start-up will be influenced by where lithium prices sit when the company is ready to make that call.

That framing tells you two things at once. Sibanye is managing execution risk carefully, which is prudent for a company entering a new commodity in a new geography. But it also means Keliber is a longer-dated option on the lithium market rather than a near-term earnings contributor. The commissioning confirms the project is advancing. It does not confirm when it will generate revenue.

Lithium market conditions entering H2 2026 remain constrained by oversupply from Australian and Chilean producers, making the threshold at which Sibanye would choose to accelerate refinery commissioning materially higher than it would have been when Keliber’s capital investment decisions were first sanctioned.

Century zinc’s cost surge and output drop show what diversification risk looks like in practice

Century’s H1 2026 result is what happens when three operational headwinds compound at a mature asset simultaneously.

The first was grade deterioration. Ore quality declined over the period, meaning more material had to be processed to produce the same volume of payable zinc. The second was adverse weather, which disrupted operations and constrained throughput. The third was scheduled maintenance, necessary work that nonetheless pulled production capacity offline during the half.

Each factor individually is manageable. Together, they pushed payable zinc output to 45,000 tonnes in H1 2026, down from 51,000 tonnes a year earlier, representing a fall of roughly 12%.

The cost line is where the damage concentrates. AISC, the all-in sustaining cost of producing each tonne of payable zinc, rose to US$2,162 per tonne in H1 2026. That is the cost figure reported in Sibanye’s trading update, with final verification due when the full interim results are released on 1 September 2026.

Century’s unit costs climbed to US$2,162 per tonne in H1 2026, up roughly 23% on the prior year, as the fixed-cost base was spread across a smaller volume of payable zinc output.

Elevated zinc concentrate prices cushioned the impact at the group level, though the extent to which that benefit filtered through to Century’s own divisional contribution will only become apparent once tomorrow’s full disclosures are available.

Zinc concentrate prices strengthened through H1 2026 as smelter disruptions in Europe and Asia tightened the refined market, which is why elevated treatment charges and spot prices provided a partial offset to Century’s cost blowout even as divisional volumes fell.

The point for investors is that Century’s headwinds are not one-off. Grade decline is structural and ongoing. Weather risk is recurring. Maintenance is necessary. These are the operational realities of a mature base metals asset, and they carry a different category of risk than the execution uncertainty at a development-stage project like Keliber.

What the two asset stories signal for Sibanye’s diversification strategy ahead of full results

Before reading too far into either asset story, the group-level picture matters. Sibanye-Stillwater guided to a more than 200% increase in headline earnings per share (HEPS) for H1 2026 versus H1 2025, alongside a swing from a prior-period loss to positive EPS.

• Group HEPS: guided to increase more than 200%, H1 2026 vs. H1 2025
• Group EPS: swung from loss to positive over the same period

Higher metals prices across the portfolio drove the recovery. That means group profitability is rebounding materially even while Century’s costs surged and Keliber remained pre-revenue. The earnings headline will look strong. The question is what sits underneath it.

Sibanye-Stillwater’s H1 2026 trading statement confirmed the more than 200% increase in HEPS and more than 560% improvement in EPS, with the Century and Keliber operational figures sitting inside a group-level recovery driven by higher metals prices across the portfolio.

Keliber and Century together are not a verdict on whether diversification is working. They are the clearest operational evidence yet of what that diversification actually requires to deliver.

Keliber represents execution risk in a new commodity, a new geography, and a demand cycle that management cannot control. Century represents the structural, recurring risks of a mature asset in grade decline. Portfolio diversification redistributes operational risk rather than eliminates it, and both assets in H1 2026 illustrate the specific forms that risk takes across PGMs, gold, battery metals, and base metals.

The full interim results on Tuesday, 1 September 2026 will provide the line-item detail, including final AISC breakdowns and divisional contributions, that clarifies how these assets net out against the group recovery. The real question those results will answer is not whether Sibanye’s earnings recovered (the guidance already confirms that), but whether the diversification assets are contributing to resilience or are currently net costs against a metals-price-driven group rebound.

Sibanye’s organic growth strategy, which targets material cost savings across the group by 2027, provides the financial framework within which the Century cost blowout and the Keliber pre-revenue phase must be absorbed, and understanding the group-level cost programme matters for reading how much tolerance management has for further divisional underperformance.

Investors who understand the operational texture of the Keliber and Century stories before those results land will be better positioned to evaluate what the divisional disclosures actually mean for Sibanye’s long-term strategic direction.

This article is for informational purposes only and should not be considered financial advice. Investors should conduct their own research and consult with financial professionals before making investment decisions. Financial figures cited from the H1 2026 trading update are subject to final verification upon release of the complete interim results on 1 September 2026.