Mount Isa Mines: A legacy of innovation and transition

After over six decades of copper mining, Mount Isa Mines will close its underground copper operations in the second half of 2025. This marks the end of an era, one that has seen Mount Isa Mines evolve from its early days into one of Australia’s most successful mining operations.

While copper production will cease, Mount Isa Mines is shifting its focus toward its long-term zinc assets, including the George Fisher Mine, which has a life expectancy until 2042, and continuing operations at the zinc-lead concentrator and lead smelter. This change represents a strategic transition as Glencore commits to investing in the region’s future and its sustainable mining practices.

A Storied Beginning in the 1920s

In 1923, prospector John Campbell Miles unearthed lead-silver ore and in 1924, Mount Isa Mines Limited was founded with the purpose of developing the discovered mineral deposits. Over the next decade, the mine developed key pieces of infrastructure including the Lawlor Shaft, Davidson Shaft, Urquhart Shaft with Headframes and Winding Plants, Mines Power Station and Rifle Creek Dam.

A significant milestone came in 1927 when diamond drilling in the Black Star lode revealed copper and in 1929, the first train pulled into Mount Isa, providing an efficient method of transport of ore and workers to the town and the mine.

Opening of the Duchess to Mount Isa Railway Branch Line, 6 April 1929

The Queensland Government was reluctant to construct a branch line from Duchess to Mount Isa as many of the branch lines that had been constructed in North West Queensland had shut down due to copper mining closures following worldwide copper prices declining after the First World War. After requests and a guarantee from Mount Isa Mines for a railway connection the branch line was opened on 6 April 1929.

In his opening speech, Mr. Reid (acting for the Chief Government Geologist) gave his expert opinion on the possibilities of the field when he said, “Conservatively a yearly output of 1,600,000 tonnes might be anticipated. A very great life was anticipated, and 100 years may be regarded as a possibility.”

World War II and Copper Expansion

In 1936, the mine had deepened enough to chase the copper ore indications and Mount Isa Mines officially transitioned into copper mining, marking a new chapter for the company.

Following more than a decade of successful lead-silver mining and smelting from 1931 to 1943, and due to the intensification of the war effort in 1942, the Australian Government's urgent need for copper to support the war effort prompted Mount Isa Mines to transition its operations exclusively to copper production. The State Government decreed that all copper ores from the Cloncurry Gold and Mineral Field was to be sent to Mount Isa Mines for treatment.

What was to follow was a remarkable period for Mount Isa Mines, this time for copper mining and smelting. In 1946, Mount Isa Mines generously contributed the final shipment of copper to the United Nations program aimed at post-war reconstruction efforts in Europe. Adjusted for inflation, this donation amounts to approximately $20 million in today's currency.

In 1949, the Copper Expansion Program commenced. With parallel production of copper and zinc-lead-silver beginning in 1953 and with this came the expansion of No. 1 Concentrator to process copper, zinc and lead as well as opening No. 2 Ore Shaft to the surface to a new ore feed system from the east side to the west side. By 1955, Mount Isa Mines was the largest mining company in Australia. It had weathered technical, financial and industrial difficulties to become Australia’s largest single creator of export income.

Between 1952 and 1960, exploration efforts substantially expanded the Mount Isa copper ore reserves, prompting Mount Isa Mines to make the strategic decision to expand its production capacity. As new reserves of copper were discovered, the Townsville Copper Refinery was established, an electrolytic refinery to produce copper cathode suitable for sale to domestic and international customers. In 1959, Mount Isa erected its iconic candy-striped Copper Smelter stack, a feat that required eight months of construction. Crafted from 200,000 firebricks imported from Argentina, the construction project incurred an estimated cost of £250,000. Operations commenced at the Black Rock Open Cut to produce copper oxide ore, serving as a flux for the copper smelter until 1963. Unfortunately, instability in its western wall prompted the premature closure of the Black Rock Open Cut in 1965.

Between 1969 and 1974, advancements in the development of copper orebodies and enhancements made at the company's Townsville Refinery led to a significant surge in copper production. Subsequently, numerous innovative technologies were pioneered on-site, catalysing a revolution in metallurgical processes worldwide.

Technological Advancements and Innovation

Mount Isa Mines was at the forefront of technological advancements in mining throughout the 20th century. In the 1980s, the company pioneered the ISASMELT™ technology and the Jameson Cell™, both of which revolutionised metallurgical processes worldwide. These innovations helped Mount Isa Mines become Australia's largest mining company during a period of growth and industry leadership.

During the late 1980s, the Deep Copper Mine underwent development, incorporating a fleet of electric-powered trucks for underground transportation. This system remained in operation until 2000, featuring an internal shaft designed for transporting copper from the Deep Copper Mine to a transfer station on U62 Copper Winder, from where it was transported to the surface. In the 1990s, The Deep Copper Mine started copper production, and the development of Enterprise Mine commenced.

In the zinc-lead mining operations, the George Fisher Mine commenced production in 2000, and the closure of the Lead Mine in Mount Isa in 2005 marked a significant milestone.

In 2012, Mount Isa Mines was named Queensland Miner of the Year and in 2013, the merger with Glencore reinforced Mount Isa Mines' position in the global mining landscape.

The Black Rock Cave project commenced in 2018 marking a change from sub-level open stoping method of mining to the caving method.

During this period, structural transformations took place involving the dismantling of the No. 2 Ore Shaft and the relocation of the R62 building along with its surrounding assets to facilitate the Black Rock Cave project. After decades of miners starting their shift from R62, X41 became the main deployment area for copper mining employees.

A Century of Legacy and Transition

In 2023, Mount Isa Mines' historical importance was celebrated as part of the city’s centennial festivities. What began with John Campbell Miles' 1923 discovery has since grown into Queensland's largest industrial enterprise.

While the celebrations marked this monumental legacy, the future of the operation took a new direction. Glencore announced that the Mount Isa Copper Operations would cease in the second half of 2025, with a renewed focus on the region’s zinc-lead assets.

By 2024, Mount Isa Mines marked its 100th anniversary. This milestone reflects a century of adapting to challenges, driving innovation, and committing to sustainable mining practices as the company looks ahead to the future.

For more information: read the September 1967 article Going deeper for Copper in MIMAG.