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During an attempt to extract iron from iron ore (magnetite), we were mostly unsuccessful. Some small grains of metallic-looking material was however present in the mixture following our attempt (see photo). This metal(?) is not magnetic. What could it be?

We used ore sampled from an abandoned quarry with the following specifications:

Main type of deposit: Iron oxide
Host rock: calc -silicate / skarn
Wall rock: Felsic volcanic rock
Age of deposit: Palaeproterozoic
Main metals: Fe, Cu, Zn, Pb, Ag

We collected the rocks using strong magnets (indicating magnetite). We then smashed them into powder and filtered out the magnetite using magnets. We then mixed it 1:1 by volume with charcoal powder and put them in an improvised crucible, which we heated using a propane torch. Most of the magnetite seemed unaffected (too low temperature I guess, since we did not have a proper, insulated furnace), although we found many silvery-gray shiny grains in the mixture afterwards (as shown in the photo). We could not see these grains before the heating. These grains are not magnetic.

What do you think that this is?

enter image description here

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    $\begingroup$ If you heat something above its Curie point, it loses its magnetism. Magnetite has a Curie point of 580 °C, well below its melting point. en.wikipedia.org/wiki/Curie_temperature $\endgroup$ Feb 12, 2023 at 21:08
  • $\begingroup$ Yes, but once it is cooled down it becomes ferrimagnetic again. All the magnetite that remained is still attracted strongly to magnets. The grains in the photo are not magnetite. $\endgroup$
    – a20
    Feb 12, 2023 at 21:10
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    $\begingroup$ My guess is that the system did not reach high temperatures. Likely lead is all you could reduce and melt .Zine boils at around 1700 F and otherwise must be protected from traces of air to refine. Lead melts about 618 F so it would be easy to evaluate it it is lead. $\endgroup$ Feb 12, 2023 at 21:28
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    $\begingroup$ If you can accurately weigh the grains and find their volume, by water displacement, you can get the bulk density of the grains and compare it to the density of various metals. $\endgroup$
    – Fred
    Feb 12, 2023 at 22:59

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First, let me start by saying that what you're doing is dangerous. You have no idea what's in the ore, whether it is volatile, if any vapour is toxic, etc. This is especially since the rocks contain lead, which can evaporate at high enough temperatures. Similar rocks often contain arsenic, and potentially mercury.

Stop doing this.

Geometallurgy operations have many safety protocols which were written in blood.

Now, to answer your question, based on your description, this is most likely either zinc, or lead, or a zinc–lead alloy. As Fred said in the comments, a density check would probably be the easiest way to do it. Lead is very dense, and zinc is also denser than both iron and copper.

There are other ways to figure out which metals are in it with all kinds of readily-available acids and other chemicals, but I will not disclose the methods because you should not be doing this.

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