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I've been looking over the internet and on here to find some kind of evidence for this, but nothing conclusive, so I was hoping for people with a better understanding of smelting, chemistry and physics to help me.

Could an early people with relatively little access to iron mines use iron oxide dust (such as ochre/ocre or… well… whatever you would call the red dust on Mars) to smelt/forge iron objects, including weapons.

If I understand correctly iron ore is technically oxidised so that should be a possibility, right?

Thanks a lot!

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    $\begingroup$ You are asking two completely different questions: iron from rust, and iron from blood. We follow a "one question per post" policy. Please modify accordingly. $\endgroup$
    – L.Dutch ♦
    Apr 11, 2019 at 15:59
  • $\begingroup$ Technically, we do something similar in Real Life. However, "natural" Aluminium can generally only be found in places like active volcanos... $\endgroup$
    – Chronocidal
    Apr 11, 2019 at 16:12
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    $\begingroup$ Agree with Chronocidal, iron ore is oxidized iron with other stuff, it even has the same red-brown color of oxide dust. Here is a link en.wikipedia.org/wiki/Iron_ore#Smelting $\endgroup$
    – Chuck Ramirez
    Apr 11, 2019 at 16:19
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    $\begingroup$ Not an answer to your question but something interesting to note, when iron (or steel as it is mostly iron) is heated, the rate it rusts at increases dramatically. Theoretically you could collect this rust as well and turn it back into useable iron. $\endgroup$
    – Liam Morris
    Apr 11, 2019 at 20:10
  • $\begingroup$ They don't need mines to have iron. Iron nuggets were (and still are) just lying around and close to the surface. Like in this video youtube.com/watch?v=SkS3N-vTZWo $\endgroup$
    – SZCZERZO KŁY
    Apr 12, 2019 at 9:06

2 Answers 2

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Yes. You will need furnace technology of, surprise, iron-age level (2500BCE, for example). A fairly pure iron-oxide dust is equivalent to an extremely high-grade iron ore. The oxides are reduced by carbon monoxide produced by burning high-carbon fuel (eg. charcoal) in a hot, low oxygen environment (eg. a blast furnace). See https://en.wikipedia.org/wiki/Bloomery

The iron compound in haematite is an iron oxide ($Fe_2O_3$) and an important iron ore... magnetite is another ($Fe_3O_4$). Any ore that contains a large percentage of either can be fed directly into a blast furnace to produce iron, and there are relatively straightfoward ways to process lower grade ores to make them useable in the same way.

Rust is commonly a mixture of hydrated iron oxides and hydroxides, and those same chemicals are found in a less concentrated form in limonite which is yet another common iron ore. You can also find stuff like bog iron from relatively shallow surface excavations. It was the major source of iron used by vikings. A major constituent is an iron oxyhydroxide, $FeO(OH)$, also found in goethite... yet another commercial iron ore.

The pigment in ochre is an iron-bearing compound like haematite, limonite or goethite, so I'm pretty certain that could be used too. The take home message should be that rust, "iron oxides" and iron ores are all more or less indistinguishable other than the kind and quantity of impurities in them.

One last comment, though.

Could an early people with relatively little access to iron mines use... the red dust on Mars to smelt/forge iron objects...

This specific case would prove tricky, as you need a supply of carbon rich fuel for the reduction processes humans use and have used. On earth, we use living trees (processed to make charcoal) or dead ones (which formed coal, then processed to make coke) and Mars has neither a biosphere nor (probably) any fossil fuels. It also didn't have any "early people", of course.

It may be that other metals are more useful on Mars if they can be refined without carbon. Aluminium and magnesium are possibilities there. There are probably also other ways to reduce iron oxide without carbon, but I'm not familiar with them.

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    $\begingroup$ This is a good answer that meets the dread hard-science mandate. +1 $\endgroup$
    – JBH
    Apr 11, 2019 at 22:19
  • $\begingroup$ Very simple, create pellets from your iron-bearing dust, and proceed as if you had lump iron ore. $\endgroup$
    – Dohn Joe
    Apr 12, 2019 at 8:26
  • $\begingroup$ I did not mean actually on Mars though, just simple red (iron oxyde) dust like the one found on Mars… $\endgroup$
    – Nierninwa
    Apr 12, 2019 at 22:46
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    $\begingroup$ @Nierninwa fair enough, just thought I'd check ;-) Martian dust is full of other interesting things which might well interfere with conventional smelting BTW... perchlorates and stuff. Anyway, this is what you get for including details without thinking about consequences! $\endgroup$
    – Starfish Prime
    Apr 12, 2019 at 22:48
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A corroded object is placed in a vacuum and electrically bombarded with hydrogen molecules, which react with the ferrous oxide, or rust. After several hours most of the rust converts to hard iron -- and the object is back to its original shape and size.

https://www.orlandosentinel.com/news/os-xpm-1986-10-19-0260290108-story.html

Some lasers are also able to reverse corrosion: https://www.youtube.com/watch?v=ACGSzBXKONo

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    $\begingroup$ "Could an early people with relatively little access to iron mines use iron oxide dust (such as ochre/ocre or… well… whatever you would call the red dust on Mars) to smelt/forge iron objects, including weapons?" Note "Early people" and "smelt/forge". $\endgroup$
    – The Daleks
    Jan 15, 2021 at 22:02

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