Mimosa Mining Company spent US$15 million on sustaining capital in the six months to June 2026 while producing fewer platinum-group metal (PGM) ounces, as weaker feed volumes and grades combined with rising costs to put pressure on the Zimbabwean operation.
According to Sibanye-Stillwater’s H1 2026 results, Mimosa’s attributable PGM production fell 7% year-on-year to 55,002 4E ounces from 59,054 ounces in the comparable period.
The decline came despite a sharp improvement in PGM prices, with Mimosa’s average basket price rising to US$2,393 per 4E ounce from US$1,317 — an increase of about 82%.
The company’s cost performance moved in the opposite direction.
Mimosa’s all-in sustaining cost (AISC) increased 23% to US$1,465 per 4E ounce from US$1,193, while operating cost rose to US$105 per tonne from US$94.
The mine also spent US$15 million on sustaining capital, compared with US$9 million in H1 2025. In rand terms, sustaining capital increased from R160 million to R245 million.
The result was a combination of higher spending and lower production: Mimosa processed 701,000 tonnes during the period, down from 723,000 tonnes a year earlier. Plant head grade fell from 3.39 grams per tonne to 3.28g/t, while recovery declined from 74.98% to 74.37%.
Yield also weakened from 2.54g/t to 2.44g/t.
Sibanye-Stillwater attributed the production decline to lower feed volumes and grade, which also affected recoveries. It said the increase in AISC was driven by inflationary increases in input costs, lower production volumes, higher royalties associated with the stronger PGM basket price and increased sustaining capital.
The report said these pressures were partly offset by movements in by-product credits.
The sales-production disconnect
One of the more striking features in the results is the divergence between production and concentrate sales.
While attributable PGM production fell 7%, Mimosa’s concentrate sales increased 32% in H1 2026.
Sibanye-Stillwater cautioned that the comparison was affected by Zimbabwe’s suspension of exports during April and May 2025. That explanation provides important context, but the gap between production and sales raises questions about the movement of concentrate between production, inventory and sales during the two periods.
The company’s published figures show that Mimosa produced 55,002 4E ounces in H1 2026, compared with 59,054 ounces in H1 2025.
Higher prices cushion the operational deterioration
Mimosa’s operational numbers are particularly notable because the mine was operating in a much stronger PGM price environment.
The average basket price increased from US$1,317 to US$2,393 per 4E ounce, yet production declined and AISC climbed from US$1,193 to US$1,465 per ounce.
In other words, the operation received substantially more for each ounce while its reported cost of producing each ounce also increased.
Sibanye-Stillwater’s figures show that the higher PGM price was therefore not enough to prevent a deterioration in Mimosa’s production and cost metrics.
Mimosa’s valuation rises as production falls
The results also reveal an unusual accounting contrast.
Sibanye-Stillwater recorded an after-tax impairment reversal of R581 million on its equity-accounted investment in Mimosa. Before deferred tax, the reversal was R783 million.
The company said Mimosa’s updated life-of-mine plan indicated higher expected future net cash flows, mainly because of increased commodity prices since December 2025.
“Mimosa’s updated life-of-mine indicated an increase in the expected future net cash flows due to increased commodity prices since 31 December 2025. The higher recoverable amount led to an after tax equity-accounted impairment reversal of property, plant and equipment
amounting to R783 million, before the impact of deferred tax (net an impairment reversal of R581 million),” the company noted.
The report itself attributes the valuation improvement to higher expected future cash flows and stronger commodity-price assumptions.
