South32 Ltd (ASX: S32) shares are sinking in early trade on Thursday after the mining giant released a detailed update on its Hermosa project in the United States.
At the time of writing, the South32 share price is down a massive 8.45% to $3.90.
Despite the stock trending lower since mid-April, it's still up around 10% in 2026.
Here's what the company released to the market.
Major update on Hermosa project
Most of the focus in this release sits with the Taylor deposit, and it gives a clearer picture of how the project is coming together.
South32 said the Taylor deposit continues to shape up as a long-life, low-cost operation with strong production potential.
One of the key changes is a longer expected mine life, which has been extended from 28 years to 33 years. That gives the project a much larger production window than previously planned by management.
The company also reported a 32% increase in mineral resources and a 52% lift in ore reserves at Taylor. Both upgrades were driven by ongoing drilling and a better understanding of the deposit.
There is also potential for future growth beyond Taylor, with the nearby Clark and Peake deposits offering additional upside over time.
Production outlook and timing
South32 is targeting first production from Taylor in the second-half of FY28.
Annual output is expected to average around 346,000 tonnes of zinc equivalent over the life of the mine. That includes zinc, lead, and silver production.
The operation is designed to ramp up to steady-state production by FY31.
From there, the project is expected to deliver consistent output for decades, supported by underground mining and a large processing facility.
Costs increase as the project moves forward
While the project is moving forward, there has been a notable increase in capital costs.
South32 now expects total growth capital expenditure of about US$3.3 billion. That is up from earlier estimates due to inflation, scope changes, and higher input costs.
Despite that, the company still sees strong economics.
At spot commodity prices, Hermosa is expected to generate around US$650 million in annual EBITDA at a steady state.
The project's net present value is estimated at around US$3.1 billion, with solid margins built into the plan.
Foolish Takeaway
There is still a long runway before production begins, so timing and cost control will be important to watch from here.
Investors will also be looking at how quickly South32 can move through construction milestones and into commissioning.
Any further updates on capital spend or timelines could influence sentiment.
Keep in mind, this is still a multi-year build, so there is an execution risk along the way.
The post This ASX 200 mining stock is sinking 8% after a big project update. Here's why appeared first on The Motley Fool Australia.
Motley Fool contributor Aaron Teboneras has no position in any of the stocks mentioned. The Motley Fool Australia's parent company Motley Fool Holdings Inc. has no position in any of the stocks mentioned. The Motley Fool Australia has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Scott Phillips.
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