Thursday, September 29, 2016

The lowest grade mines in the world - Copper

I've received a lot of requests from people to look at different projects and verify their quality. Some projects are easy (North Bullfrog, San Diego, Cerro Las Minas), they are very low grade, but carefully created equivalents grades calculated from basically any metal content in the rock and assuming 100% recovery.

While I was working on these projects I started to build up a database from actual operations is to try and find the lowest grade mines by:
  1. Commodity
  2. Mine type (open pit vs underground)
This will allow you to quickly check the grade from drill-holes and 43-101 resource calculations from your favorite projects to see how they stack up. However, many of these mines have been in operation for a very long time and originally the operations commenced by mining high grade or leachable ores before transitioning to lower grade ores that they are mining now.

This list will be dynamic and send me some info on other project that you feel should be on this list, please send me some information and I'll update it.

I've also compiled a small list of 'development projects' that include mines currently under construction or being presented a project that could go into production in the not to distant future (i.e. we have a PEA or feasibility study).

Open Pit

  1. Mount Milligan, Canada - Thompson Creek Mining (porphyry deposit operated at 54,000 tpd)
    • Grade* - total mineral reserves from Dec 2015 (link)
      • Cu = 0.196% (note - grade mined in 2015 was 0.38% Cu)
      • Au = 0.349 g/t
      • * - reserves were calculated at $2.95/lb Cu and $1250/oz Au.
    • Basically this is a gold mine with copper credits.
  2. Aitik, Sweden  - Boliden (Porphyry, operating at 36,500 tpd)
    • Grade - 2015 production grades from 2015 annual report (link)
      • Cu = 0.23%; 
      • Au = 0.15 g/t
      • Ag = 0.13 g/t
      • Mo = 0.002%
    • Easily accessible ore (low strip ratio), highly automated and uses large mining equipment that makes the mine most productive open pit copper mine in the world (tonnes of ore produced per employee).  Low treatment charges - concentrate sent to Boliden smelter in Ronnskar (link). Gold an important by-product
  3. Sierrita, AZ, USA - Freeport (porphyry, operated at 102,000 tpd)
    • Grade - reserves (Freeport 2015 10K (link).
      • Cu = 0.24%
      • Ag = 1.42 g/t
      • Mo = 0.03%
    • Operating at reduced capacity (link)
  4. Mount Polley, Canada - Imperial Metals (porphyry deposit operated at 20,000 tpd)
    • Grade* - total mineral reserves from Jan 2014 (link)
      • Cu = 0.295%
      • Au = 0.302 g/t
      • Ag = 0.615 g/t
    • Mine restarted in Aug 2015 after tailings dam failure in Aug 2014.
  5. Constancia, Peru - HudBay (porphyry operated at 81900 tpd)
    • Grade - Jan 2015 reserves (link)
      • Cu = 0.30%
      • Au = 0.054 g/t
      • Ag* = 2.97 g/t
      • Mo = 0.009%
    • *Silver Wheaton acquired life of mine silver production from Constancia in April 2012 (link)
  6. Pinto Valley, AZ, USA - Capstone (porphyry deposit operated at 54,000 tpd)
    • Grade - total mineral reserves from Jan 2016 (link)
      • Cu = 0.31% (note - grade mined in 2015 was 0.38% Cu)
      • Mo = 0.009%
    • Capstone purchased this as an operating mine from BHP for US$650M (link)


  1. Bolivar, Mexico - Sierra Metals (Cu-Zn skarn operated at 2500 tpd)
    • Grade - April 2013 reserves (link)
      • Cu = 0.76%
      • Zn = 0.33%
      • Au = 0.23 g/t
      • Ag = 19.52 g/t
    • Polymetallic mine, with a CuEq grade of 1.04%
  2. Pyhasalmi, Finland - First Quantum (VMS deposit mined at 1000 tpd)
    • Grade - data from FQM website (link)
      • Cu = 0.9%
      • Zn = 1.9%
    • Note: the Pyrite they produce is also sold as a fertiliser.
  3. Surda, India - India Resources (shear hosted copper deposit operating at 2200 tpd)
    • Grade - June 2013 resources (link)
      • Cu = 1.1%
    • I couldn't find much information on this deposit, but this PR (link) suggests that they will be putting the mine on care and maintenance in the near future. No byproduct production, only copper.
  4. Cozamin, Mexico - Capstone (mesothermal Cu-Zn vein operating at 3300 tpd)
    • Grade - Jan 2016 reserves (link)
      • Cu = 1.5%
      • Zn = 0.71%
      • Pb = 0.17%
      • Ag* = 42 g/t
    • *Silver Wheaton purchased the 100% of silver production from Cozamin, but the project is located in one of Mexico's largest and richest silver districts (Zacatecas Mining district with estimated historical production since 1546 of  >1Boz Au and ~10Moz Au) from high grade veins. It will be interesting to see if Capstone start mining high grade silver ores once the royalty agreement expires?

Development projects

  1. Tepal Project, Mexico, Geologix (porphyry copper-gold, 38,700 tpd open pit mine)
    • Grade - Jan 2016 reserves (link)
      • Cu = 0.2%
      • Au* = 0.3 g/t
      • Ag* = 1.54g/t
      • Mo = 0.004%
    • Relatively low strip ratio, good byproduct Au values.A very poor location to have a project as the area is controlled by the Nights Templar Drug gang.
  2. Santo Domingo, Chile - Capstone Resources (porphyry copper, 65000 tpd open pit mine)
    • Grade - Jan 2016 reserves (link)
      • Cu = 0.3%
      • Au = 0.04 g/t
      • Fe = 28.2%
    • Capex = $1.7B
    • How much will the iron contribute to revenues?
  3. Calingiri, Australia - Caravel Minerals (Copper porphyry, 43,000 tpd open pit operation)
    • Grade - April 2016 reserves (link)
      • Cu = 0.34%
      • Au* = 0.02 g/t
      • Ag* = 1.8%
      • Mo = 0.008%
    • Capex = AU$440M
  4. Cobre Panama, Panama - First Quantum Minerals - 80% ownership (porphyry copper, 200-250,000 tpd open pit mine)
    • Grade - Jan 2016 reserves (link)
      • Cu = 0.38%
      • Au* = 0.07 g/t
      • Ag* = 1.3g/t
      • Mo = 0.006%
    • Capex = $5.95B
    • Note: Mining will focus on higher grade core. Precious metal stream sold to Franco Nevada. This project is currently in development.

One of these days i'll calculate the CuEq grades for these projects



  1. One thing AG. Pinto Valley is for sure an IS operation. (In situ copper leach) As an aside the water table under Pinto Valley is corrupted just like EVERY OTHER IS operation in the world. Radiometric ore gets enriched with the 'recycling of the raffinate' and tis leachable. The propaganda about sulfuric acid being like 'lemon juice' (the first time through) is pure bullchit. Horrid terrible on the world are IS operations.

  2. My bad. Tis appearing Capstone is back with the oxides, making not too much off it by the looks of it. BHP took on the sulfides via IS up to late 2013.

    1. BHP did well to sell the mine when they did! I'll do a post on the difference between different ore zones and explain what they meet for processing and recovery for each metal

    2. Capstone is losing millions so one wonders, very mightily, why they would be depleting their resources (2015 Grade* (Cu% 0.38) for no apparent gain. Turds might try IS again, that reduces operating costs significantly. BHP was the big winner unloading Pinto at these depressed Cu levels I suppose. Unreal 'investment' by those abject tards.

  3. You might want to consider some of the RTB Bor operations in Serbia. Cerovo open pit may be reopening with a copper grade of 0.31% and Veliki Krivelj is currently operating with a remaining reserve grade of 0.323% copper. The Jama underground mine is also low grade.

    1. Will do, do you have any hints for low grade open pit silver mines except Rochester in Nevada?

  4. We got double diamonds today. PSJ talks about purple diamonds

    whilst CSJ talks about red diamonds and the Rio Tinto tenders.

  5. Gold exploration I think this is an informative post and it is very useful and knowledgeable. therefore, I would like to thank you for the efforts you have made in writing this article.

  6. This post is informative for copper lover.
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