South African mining input costs rose 4.9% year-on-year in September 2026, up from 3.7% in August, and fuel is the main culprit. That's the headline finding from the Minerals Council South Africa's (MCSA) mining composite input cost index (a basket tracking what producers pay for everything from diesel to chemicals), and it lands at an awkward moment for the sector's planners.

The 1.2 percentage-point acceleration ends a brief moderation. August had offered a little relief. September took it back, and the composition of the increase points squarely at energy.

Where is the pressure coming from?

Coke and refined petroleum costs climbed 8.6% month-on-month and 32.9% year-on-year in September, reversing August's modest monthly decline. The category carries real weight: it accounts for 5.51% of total mining input costs, so a move of that size drags the whole composite index upward. Other chemicals (0.28% of the basket) and basic chemicals (2.30%) matter far less, even when their prices jump. Other chemicals and artificial fibres also showed pronounced cost pressure.

Here's the mechanism worth understanding. A category's price increase is not the same as its contribution to the index — that contribution depends on the category's weight in the input basket. Fuel is heavy in that basket. It's also contagious, because fuel pressures can spread beyond direct purchases into suppliers' transport and delivery charges. Miners face a double exposure: immediate expenditure increases now, and cost-push increases later as contracts are repriced.

Why do the US midterms matter to a mine in Rustenburg?

Two channels. First, fuel itself: relief in fuel prices is what the sector is watching, and US political shifts feed through global oil markets. Second, interest rates. Changes in US rates can move the rand-dollar exchange rate, which has stayed stable since the elections. That stability isn't guaranteed.

The arithmetic cuts both ways. Rand depreciation raises the local-currency cost of imported fuel, machinery and other inputs. Appreciation delivers cost relief, but it shrinks the rand value of dollar-denominated export receipts. There is no free lunch on either side of the trade.

The midterms themselves delivered a split verdict: the Democrats took both the Senate and the House, gaining control of Congress for the remainder of Donald Trump's presidency.

What does the Agoa exclusion change?

A separate headache. The US has put South Africa on notice that it will be excluded from the African Growth and Opportunity Act (Agoa) — the scheme giving eligible sub-Saharan African countries preferential, largely duty-free access to the US market for thousands of products — as of January 2027.

The exposure is uneven across the economy. Affected exports include motor vehicles and automotive components, citrus and other agricultural products. Raw minerals and metals exports escape untouched, because they generally don't rely on Agoa to reach US buyers. For miners, the exclusion is a macro concern rather than a direct tariff hit — but it lands on a national economy already under strain.

Is any commodity escaping?

Not really. Annual input cost increases ran at least 4% across every commodity group in the brief. Other mining and quarrying, coal and gold all posted increases above the sector average of 4.9%. Iron ore and manganese sat 0.5 percentage points below the aggregate rate; other metallic minerals and chrome, 0.4 points below. Those gaps are narrow. This is a sector-wide cost problem, not a commodity-specific one.

One caveat on interpretation. Commodity-level cost inflation doesn't tell you which producers face the greatest financial strain — margin outcomes also depend on output prices, production volumes and operating efficiency. And since mining is predominantly a price-taker, higher input costs inevitably squeeze profit margins and, among other effects, reduce corporate income tax receipts for the fiscus.

What happens next?

Each operation's outcome will hinge on its input mix, procurement arrangements and its ability to offset higher costs through productivity gains or stronger realised selling prices. The principal risks the brief flags are further fuel-cost pass-through, exchange-rate volatility, and persistent uncertainty over international trade and energy supply.

September's message is blunt: the cost squeeze is back, petroleum and chemicals are leading it, and nobody in the commodity complex is immune.