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The Democratic Republic of the Congo's Katanga Province contains almost 40% of the world's reserves of cobalt [1].

Why are deposits concentrated so strongly in such a small portion of the earth?

I would have thought that this is due to similar reasons to: Why do gold deposits form only in certain areas of the earth?

But the distribution of cobalt seems far more uneven than that of gold.

Do the geological processes causing this uneven distribution significantly differ from those that cause the uneven distribution of gold?

[1]: British geological survey, 2009

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Part 1

The Democratic Republic of the Congo's Katanga Province contains almost 40% of the world's reserves of cobalt [1].

Why are deposits concentrated so strongly in such a small portion of the earth?

Cobalt isn't as unevenly distributed as it seems. It is correct that most of the world's cobalt reserves are in DRC, but most of the cobalt resources are not in DRC. And this is a very important point.

Resources are known and estimated quantities of economically extractable materials. Reserves are resources for which detailed plans for extraction have been made. This means that to turn a resource into a reserve you need to have plans for the extraction and refining plants, have environmental approval, have the workforce figured out, have authorisation from the owners of the land, and more. As you can guess, making a resource into a reserve is a time consuming and expensive process.

The reason why most of the Earth's reserves are in DRC is simply because it's easier and cheaper. The infrastructure already exists, and the expertise exists. At current technology levels and cobalt prices, the investment in defining a reserve from a resource elsewhere is simply not economical.

This does not mean that DRC has most of the cobalt. It only means that getting cobalt out of the ground and making it into a product is cheaper in DRC than it is in other countries.

Part 2

Do the geological processes causing this uneven distribution significantly differ from those that cause the uneven distribution of gold?

The reasons are the same, in principle. Every element behaves differently and will separate from other elements and concentrate because of various geological processes. Cobalt tends to follow copper and nickel, and in most cases it is mined as a by-product of those elements. That's why cobalt is extracted from the African Copperbelt, and why it's extracted from nickel deposits in Australia. Not much point going into the chemistry and thermodynamics of why this happens, but the point is that elements which are concentrated by rare geological processes will be found in fewer places, and elements that are concentrated by common geological processes will be found in more places.

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    $\begingroup$ "Reserves vs resources" Seems like this is the same conversation as to when we start pulling oil from the Tar Sands in Canada - we know it's there but it's only used when prices are above X (because it's not profitable under a certain price) $\endgroup$
    – WernerCD
    May 18, 2021 at 4:38
  • $\begingroup$ I guess we don’t know half of what is beneath the oceans, but above sea level, what processes are concentrating certain elements to specific places? $\endgroup$
    – Jonathan
    May 18, 2021 at 7:54
  • $\begingroup$ @Johnny that's more than can fit in a StackExchange answer, and dependent on element. There were many books and papers written about these topics. $\endgroup$
    – Gimelist
    May 18, 2021 at 11:25
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    $\begingroup$ Where would be a good basic starting point to learn more about this? $\endgroup$
    – Jonathan
    May 18, 2021 at 12:23
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    $\begingroup$ @Johnny usgs.gov/centers/nmic/minerals-yearbook-metals-and-minerals that would be a start $\endgroup$
    – Gimelist
    May 19, 2021 at 1:31
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Its not that cobalt is less abundant or wide spread. What you are noticing is that gold has been mined for far longer than cobalt and is far more valuable. Gold has been mined even in antiquity and even poor deposits are usually worth extracting, so most of the large easy deposits were mined out ages ago.

Cobalt on the the other hand was only discovered in the early 1700's and has far less value. We still have big easy to mine deposits of cobalt and the lesser deposits are not worth mining, so we only mine the easiest places to extract it.

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    $\begingroup$ Also, just like silver, cobalt is usually a byproduct of mining other valuable metals (copper and nickel, mostly). The best grades of cobalt "ore" still contain something like 0.2-0.7% of cobalt, while the copper in the same ore is somewhere around 3-5x times as abundant. This also necessitates much processing near the mine - you don't want to ship such low-grade ores. Funnily enough, the tailings from the old (less efficient) mining operations are now regularly being processed - they have higher grades than the currently mined ores :) $\endgroup$
    – Luaan
    May 17, 2021 at 8:09
  • $\begingroup$ For a bit of scale, the gold deposits mined in the Carlin Trend (Nevada) contain 0.2-0.25 ounces of gold per ton of ore. That's 0.001% or less. So for gold, an economically mineable ore is much less concentrated than one might think. But gold is currently at $1867/oz, cobalt at $1.38. $\endgroup$
    – jamesqf
    May 17, 2021 at 17:21
  • $\begingroup$ Yeah, but that kind of "mine tons to get an ounce" problem is par for the course with gold. When you look at historic outputs of old mines, gold mines typically get many, many times the amount of silver per unit of gold they get. $\endgroup$
    – Harper - Reinstate Monica
    May 17, 2021 at 18:47
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    $\begingroup$ @Harper - Reinstate Monica: I don't think that's true of all gold mining - certainly not the placer mining of various gold rushes - though Nevada's Comstock Lode silver mines started out as gold mines, until some curious person wondered what that grey mud was :-) But my point was that if cobalt was as valuable as gold, there'd probably be a lot more low-concentration deposits that would be considered workable ores. $\endgroup$
    – jamesqf
    May 18, 2021 at 4:33

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