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I have had this for over 20 years and I still don't know what it is. I found it on top of the ground by my dad's workshop in our yard in Louisiana. I don't know how it got there. It weighs 6 pounds 7 ounces (2.92 kg). It's very shiny and has never dulled in the 20 years I've had it. It's very hard. I couldn't chip it with a hammer. Photos included. Monster can for scale.

picture of rock picture of rock with can

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Based on the brassy color, it's metallic luster, and it's resistance to breakage, I would say it's pyrite. Try to scratch glass with it (be careful not to break the glass). If it scratches, it is likely pyrite. If a nail can't scratch it, it is likely pyrite. You could test it's streak by rubbing it on a piece of hard unglazed ceramic. If it leaves a black mark (maybe with a hint of green), then it is likely pyrite.

https://en.m.wikipedia.org/wiki/Pyrite

Edit: Based on a approximate volume of 458 mL (that of the Monster), which is 458 cm3, and the density of pyrite of 5 gm/cm3, then sample should weigh about 2.3 kg (5 lbs). Galena (see wienein comment below), a less brassy and less hard (easier to scratch) metallic mineral, has a higher density of 7.6 gm/cm3, which would give is a mass of 3.5 kg (7.7 lbs), closer to what you are showing in the picture. Galena has a light grey streak and contains lead.

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    $\begingroup$ I agree that it is likely pyrite, but since the pictures seem to have a yellow tint galena might be possible as well. Hardness and streak should clarify that $\endgroup$ – wienein Jan 26 '16 at 14:43
  • $\begingroup$ Would it be wise (given that we have these candidate materials) for the OP to measure its actual volume by submerging it in water? We could then calculate the actual density. $\endgroup$ – Jan Doggen Jan 26 '16 at 16:10
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    $\begingroup$ There is also the assumption that the material is homogenous, and not comprised of multiple minerals. $\endgroup$ – Inkenbrandt Jan 26 '16 at 16:19
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    $\begingroup$ Based on those observations, I am leaning towards galena. Make sure you wash the knife thoroughly, as galena is a lead-based mineral. If the sample is easy to scratch with a nail, and if it is more silver than brassy, then I would definitely say galena. $\endgroup$ – Inkenbrandt Jan 26 '16 at 21:59
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    $\begingroup$ @Vhdn If you find my answer as acceptable, please mark it as the accepted answer, unless you are awaiting more information. $\endgroup$ – Inkenbrandt Jan 28 '16 at 17:35

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