page_title: Mount Isa Mines
section_title: The lean years (1924–1945)
hierarchical_section_title: Mount Isa Mines / History / The lean years (1924–1945)
caption_attribution_description: English: Arrangement of D &amp; L machinery in the smelter, Mt. Isa Mines, 1932
context_page_description: Mount Isa Mines Limited operates the Mount Isa copper, lead, zinc and silver mines near Mount Isa, Queensland, Australia as part of the Glencore group of companies. For a brief period in 1980, MIM was Australia's largest company. It has pioneered several significant mining industry innovations, including the Isa Process copper refining technology, the Isasmelt smelting technology, and the IsaMill fine grinding technology, and it also commercialized the Jameson Cell column flotation technology.
context_section_description: The early years were characterized by the struggle to develop the lead–zinc ore bodies, including the need to finance drilling, metallurgical test work and shaft sinking, and there was significant doubt that Miles' discovery would ever amount to much. However, by the end of 1928, the drilling had allowed an estimate of reserves of 21.2 million tons, which were at the time the largest in Australian history, and rose to an estimate of 32 million tons in 1930.
  Crucial to the success of any mining venture was a rail line connecting the area to the coast. However, the Queensland Government was reluctant to invest in a railway to what might be a mine of limited life. After the mining company guaranteed to cover any losses, construction of the railway from Cloncurry to Mount Isa began in 1926, and the line opened on 27 May 1929, giving Mount Isa an essential link to Queensland's eastern seaboard.
  The cost of developing the Mount Isa ore body was so high that the owners had to turn to ASARCO to obtain sufficient finance to bring the operation into production. The project was running behind schedule and over budget, which ultimately resulted in ASARCO sending its own man, Julius Kruttschnitt II, to take charge. Kruttschnitt arrived in 1930 to find that bills were going unpaid because there was no money to pay them, the shafts were flooding, and the construction of the surface plants was months behind schedule.
  When mining commenced in 1931, the mine was mechanized to an extent not previously seen in Australia, with mechanized drilling and mechanical shovels rather than "hammer and tap" hand drilling and hand shovels. The initial mine production was 660,000 tonnes per year ("t/y") of ore and stayed at about this level until 1953.
  Even after the first ore had been mined and processed, the Mount Isa operations struggled. The smelter proved inadequate and required a third blast furnace and additional sintering machines. The recovery of valuable minerals in the concentrator was less than expected, and the metal prices were depressed by the Great Depression of the 1930s. The poor recoveries were found to be caused by the unusually (for the time) fine nature of the mineral grains in the Mount Isa ore. While the metal prices eventually recovered as the Depression passed, the fine mineral grains were to plague the Mount Isa lead–zinc operations for the rest of their days.
  By June 1933, the debt owed by MIM to creditors around the world, £2.88 million, was equal to 15% of all income tax paid in Australia in 1932. It was not until the 1936–1937 financial year that MIM made its first profit and the company could begin to pay down its burden of debt. However, the outbreak of The Second World War was not kind to MIM, because it could no longer find markets for all its production, and the price of lead did not increase as it had during the First World War.
  While some copper mineralization had been discovered during drilling in the late 1920s, the major find did not come until 1930, when drilling to explore the lead–zinc ore body passed through almost 38 meters of copper mineralization with an average grade of 4.3% copper. While this was a very good grade, MIM did not have the financial resources to develop the copper, and it was not until global copper prices increased in 1937 that there was an incentive for further copper exploration. These efforts were initially unsuccessful, but yielded fruit in 1940 and 1941. However, it was not until 1941–1942 that mining of the No. 7 level of the Black Star lead-zinc ore body allowed the existence of an economic copper deposit to be established.
  MIM was still not in a position to mine the copper, because it had stockpiles of lead bullion and zinc concentrate that could not be sold due to the war. However, the Australian government needed copper for its war effort and lent MIM £50,000 to allow the mining to proceed. Further drilling expanded the copper reserves and MIM decided to switch from lead to copper production. The lead–zinc concentrator could treat the copper ore with little modification, but the l
caption: The sinter machines in the Mount Isa lead smelter, 1932.
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