Transforming McArthur River Mine: How IsaMill™ Redefined Grinding Technology in the Northern Territory

In Australia’s Northern Territory, the McArthur River Mine is one of the world’s largest zinc, lead, and silver deposits. But for decades, its economic viability was limited, not by the scale of the deposit, but by the complexity of its ultra-fine-grained ore. That all changed with a leap in grinding technology.

At Glencore Technology, we’ve always believed in transforming challenges into opportunities. This is the story of how our horizontal grinding mill, IsaMill™, delivered a breakthrough in efficient ore grinding, enabling sustainable mineral processing at McArthur River. It's also a story of how mining innovations in Northern Australia are shaping the future of the global industry.

Why McArthur River Was a Challenge Unlike Any Other

Discovered in 1955, the McArthur River deposit was rich in zinc and lead but went undeveloped for over 40 years. The reason? No grinding technology could efficiently reduce the ore to the fine sizes needed for economic recovery. Traditional tumbling mills, such as ball or tower mills, consumed excessive energy, used costly steel media, and created problems for downstream flotation.

With increasing pressure to treat finer and more complex deposits across the mining industry, especially in Northern Australia, it was clear that a new approach was needed.

The Breakthrough: A Horizontal Mill With Manufacturing Origins

The turning point came from outside the mining industry. The head of research at Mount Isa, Bill Johnson, recognised that other sectors like pharmaceuticals, inks and even chocolate manufacturing had long been solving the challenge of fine grinding.

Partnering with Netzsch, leaders in fine grinding for manufacturing, we adapted horizontal stirred milling for mineral processing. This required a complete redesign to meet the needs of large-scale mining operations: robust construction, continuous operation, and the use of low-cost or recycled grinding media.

The result was the IsaMill™, a horizontal grinding mill that delivers high-intensity, energy-efficient, and inert grinding in a compact footprint.

The IsaMill™ stepped up once again.

Through extensive lab and pilot testing, our engineers proved that IsaMill™, using newly developed MT1 ceramic media (by Magotteaux), could efficiently grind coarser material directly from the SAG mill. This marked a shift in perception: IsaMill™ was no longer just for regrind, it was now a viable, powerful tool for mainstream coarse grinding.

The New Circuit: A Smarter Way to Grind

The expansion project saw the installation of two 3 MW M10,000 IsaMills in open circuit configuration, grinding the SAG mill screen undersize to 45 microns before flotation. This change:

• Eliminated the need for Tower Mills and cyclones,

• Increased plant throughput by 33% (from 2.4 Mt/y to 2.5 Mt/y).

• Improved flotation performance due to finer, more uniform feed,

• And enhanced sustainability through reduced reagent use and lower power consumption.

This transformation highlighted the power of IsaMill™ to enable sustainable mineral processing at scale.

Leading Mining Innovations in Northern Australia

The initial McArthur River mineral recovery was a success that's now a reference point for mining innovations in Northern Australia. It demonstrated how technology can unlock value from complex ore bodies while reducing environmental footprint. These are goals that are increasingly central to modern mining projects.

It’s not just McArthur River. Other operations, like Anglo Platinum, implemented IsaMill™ technology across multiple sites, enhancing their processing capabilities and confirming that horizontal stirred milling is a cornerstone of modern grinding technology. Read more about IsaMill™ at Anglo Platinum [PDF].

Key Takeaways for the Industry

For anyone in mineral processing, particularly in regions dealing with fine or difficult ores, McArthur River offers critical lessons:

1. Innovation can come from unexpected places – even chocolate mills.

2. Horizontal mills offer unique performance and scalability benefits over traditional grinding.

3. Energy-efficient grinding is not just possible, it’s commercially proven.

4. Inert grinding environments improve downstream flotation, reducing chemical use.

5. IsaMill™ is versatile: suitable for both fine regrind and coarse grinding.