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You are walking in the mountains and pick up what looks like a nugget of gold. You're aware that fools gold (iron pyrite, $\ce{FeS2}$) exists. Create an experiment to test if this is pure gold or iron pyrite.

The simplest thing I could think of is to do a magnetic test on the assumption that if it was fools gold it would be attracted to a magnet due to the presence of iron. A quick google search reveals this to be true but I have a sneaky suspicion that I got lucky in assuming, because there is iron in $\ce{FeS2}$ the compound will be magnetic.

I'd like to know if chemical compounds retain the properties of their individual elements or if the compound gains completely new properties some of which may or may not be properties of the elements.

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    $\begingroup$ As a general rule, compounds do not retain the properties of their elements. A classic example is NaCl, as discussed here $\endgroup$
    – bon
    Sep 17, 2015 at 9:26
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    $\begingroup$ Simplest way is density - pyrite is about 4 times less dense than gold, lighter than pure iron. $\endgroup$
    – Mithoron
    Sep 17, 2015 at 10:21

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Pyrite is not magnetic. Some related minerals are, but only weakly, not as strong as iron, so the test will likely fail anyway. Magnetism is not an inherent property of an element, but that of a compound. Most compounds of iron are not magnetic (though some are); on the other hand, there are organic magnets made out of totally non-magnetic elements.

Think of something based on chemical properties instead. Pyrite is a salt of a metal and a weak acid. Gold is a metal, of the kind that would not react with acids. See where this gets you.

As for the other properties of the elements, some would be inherited by their compounds and some (arguably, most of them) would not.

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  • $\begingroup$ +1 for the organic magnets. I didn't hear about them before. It is quite an interesting information. Just found this nice review on organic magnets. $\endgroup$
    – WYSIWYG
    Sep 17, 2015 at 19:17

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