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I wondered, in general, what has happened to all the minerals that have been mined by humans. Do they still circulate in the economy and could be recovered through 'urban mining'. Or will they have corroded or otherwise reacted with the environment and no longer exist in a form that could be easily recovered?

I appreciate it's a broad question. I might be helpful to discuss a single mineral as an example.

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    $\begingroup$ What do you want the answer to be ? $\endgroup$
    – blacksmith37
    Oct 11, 2022 at 16:40
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    $\begingroup$ @blacksmith37: that is a reply I'd expect a metallurgist to give. :-) It's basically the punch line of a joke I here more than 30 years ago. Ask a geologist what's 2+2 & the answer you get, with a bit of head scratching is a prolonged, "something between 3 & 5". Ask a surveyor what's 2+2 & the answer you get back is 3.9999. Ask a metallurgist what's 2+2 & the metallurgist will then reply "what would you like it be?". $\endgroup$
    – Fred
    Oct 11, 2022 at 17:16
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    $\begingroup$ voting to close this is a textbook example of "needs more focus" any reasonable answer would be a thesis document. $\endgroup$
    – John
    Oct 12, 2022 at 20:48

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The answer is, "it depends on the minerals and what happened to them once they were mined".

There are two types of minerals mined: ore minerals and waste minerals. To mine ore minerals invariably waste minerals must also be mined. Waste minerals typically encapsulate orebodies. To mine the ore, some of the waste must be mined as well. For reasons of safety, stability and practicality, the walls of open pit mines cannot be vertical. They have to be sloped. Because of that, some waste must be mined to get access to the ore.

Similarly with underground mining, not all the tunnels will be mined in ore. To access the ore, some tunneling will be done in waste.

Depending on the geology of the deposit, most waste minerals will be silicates, such as the minerals within basalt, etc. The waste rock will either be dumped onto a waste dump on the surface and very slowly oxidize over time, or they will be used to backfill stopes, underground, that once contained ore minerals. In vary rare instances some of the minerals will be used as road construction materials. As for ore minerals they must first be processed to concentrate the ore minerals. The associated waste minerals from the processing plant usually end up in a tailing dam and will slowly oxidize over time. In more recent times, at some mines, some of the minerals that are larger than 200 μm in size have been returned as paste fill to the voids from which ore minerals were extracted.

There are basically two types of ore minerals: oxides and sulfides. From these, the metals of interest will be extracted: iron, zinc, copper, tin, lead etc. In the past, the unwanted sulfide minerals may have been converted to sulfur dioxide and released into the atmosphere. Some of it may have been used to make sulfuric acid. Some of it has been dumped and is slowly oxidizing and forming sulfuric acid in the environment, to the detriment of the environment.

In the past, some sulfide ores have been burned as a fuel to rapidly oxidize the minerals to make downstream extraction of the desired metal easier. Such burning produced vast quantities of sulfur dioxide which produced acid rain, which then kill the surrounding vegetation resulting in a denuded and much damaged landscape.

Eventually, most metals that have been extracted from minerals will oxidize over time.

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  • $\begingroup$ Thank you - very helpful. In simple terms, what happens when they oxidize? Does that mean they end up in a consistency that could theoretically be recovered for human use, but only with significant energy or technological input - or will they be lost for practical purposes. $\endgroup$
    – sba222
    Oct 12, 2022 at 17:15
  • $\begingroup$ Generally, metal oxides are easier to treat than sulfides, but there are always exceptions. Nickel oxides tend to be more difficult to treat (to obtain nickel metal) than nickel sulfides. Similarly all iron mined for iron & steel products are sourced from iron oxides. This is also due to more iron oxides being naturally available than iron sulfides & the iron oxide deposits being significantly larger. Iron sulfides have been mined for the sulfur, not the iron. I know of one location where this occurred during World War II so that the sulfur could be used to make gun powder. ... $\endgroup$
    – Fred
    Oct 12, 2022 at 18:04
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    $\begingroup$ ... More recently, sulfur from iron sulfides has been used to produce sulfuric acid & sometimes that acid has been used to super phosphate agricultural fertilizers. The issue with metals oxidizing over time & then treating those oxides to re-obtain the metal for useful products is the dispersion of the oxides makes the economics of treating them more expensive than mining large naturally occurring deposits of minerals. $\endgroup$
    – Fred
    Oct 12, 2022 at 18:12
  • $\begingroup$ Thanks this last comment in particular is what I'm aiming at. So, for example in the case of iron, oxidized iron could be recovered, but it's dispersed and therefore more energy/technology intensive to recover? $\endgroup$
    – sba222
    Oct 14, 2022 at 8:09
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    $\begingroup$ @sba222: Summed up nicely. $\endgroup$
    – Fred
    Oct 15, 2022 at 0:26

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