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Some observations on copper yields and ore grades

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  • Crowson, Phillip

Abstract

The paper examines trends in the average copper content of mined ores over the years. It has tended to decline over the long term, but by no means evenly. US averages are not typical of global averages, at least in the past four decades. Those have been both higher, and less volatile than in the US. One reason for falling averages is a change in the type of deposit mined, with a rise in the share of relatively low grade porphyry deposits. The different nature of their deposits is reflected in marked differences in grades between the different continents. African and Australian average grades are higher than the global average, and changes in the share of Central Africa in global output have affected the global average grade. Yields are have been consistently lower in North America than elsewhere, and Latin American average grades have trended downwards, reflecting both the ageing of mines and the rising share of production from porphyry deposits. Typically the yield of mines declines over time as mining proceeds. The average copper content of ore deposits is usually below the average yield of the ore accessed in the early years of production. The initial grades of new mines have not declined over the past forty years, and there has been no perceptible tendency for the average grade of porphyry deposits brought into production to decline over time. There is no apparent correlation between average grade and deposit size, but mine operators tend to exploit economies of scale to offset low grades. The relationship between the annual percentage yields (the head grade) and the reserve grades of deposits is not static. In recent years head grades have fallen closer to reserve grades. The relationship may be affected by movements in metal prices. Although the evidence about the influence of prices is not clear-cut, it does suggest that prices and cut-off grades may be inversely related. As many ores contain other valuable metals besides copper, copper yields will sometimes be subordinated to the extraction of these other metals. Copper equivalent grades have not moved in the same way as copper grades alone.

Suggested Citation

  • Crowson, Phillip, 2012. "Some observations on copper yields and ore grades," Resources Policy, Elsevier, vol. 37(1), pages 59-72.
  • Handle: RePEc:eee:jrpoli:v:37:y:2012:i:1:p:59-72
    DOI: 10.1016/j.resourpol.2011.12.004
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    References listed on IDEAS

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    1. Crowson, Phillip, 2003. "Mine size and the structure of costs," Resources Policy, Elsevier, vol. 29(1-2), pages 15-36.
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    Cited by:

    1. R. H. E. M. Koppelaar & H. Koppelaar, 2016. "The Ore Grade and Depth Influence on Copper Energy Inputs," Biophysical Economics and Resource Quality, Springer, vol. 1(2), pages 1-16, December.
    2. Ousman Gajigo & Mouma Ben Dhaou, 2015. "Working Paper 222 - Economies of Scale in Gold Mining," Working Paper Series 2161, African Development Bank.
    3. Fizaine, Florian & Court, Victor, 2015. "Renewable electricity producing technologies and metal depletion: A sensitivity analysis using the EROI," Ecological Economics, Elsevier, vol. 110(C), pages 106-118.
    4. Victor Court & Florian Fizaine, 2014. "Energy transition towards renewables and metal depletion: an approach through the EROI concept," Post-Print hal-01411803, HAL.

    More about this item

    Keywords

    Copper; Ore grades; Yields; Reserves; Prices;

    JEL classification:

    • L72 - Industrial Organization - - Industry Studies: Primary Products and Construction - - - Mining, Extraction, and Refining: Other Nonrenewable Resources
    • N5 - Economic History - - Agriculture, Natural Resources, Environment and Extractive Industries
    • Q30 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Nonrenewable Resources and Conservation - - - General
    • Q39 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Nonrenewable Resources and Conservation - - - Other

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