I have the following rock/mineral but can't seem to identify. Anybody have an idea what it might be? It's heavy, 3"x3", nonmagnetic (but slightly repels a neodymium magnet), blackish in color with thin brassy crystals. Thanks!

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closed as unclear what you're asking by gerrit Nov 2 '18 at 12:28

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  • $\begingroup$ Nice specimen. It might be something unusual. Do you have a location for the specimen? $\endgroup$ – Gary Kindel Oct 17 '18 at 1:42
  • $\begingroup$ Unfortunately no. It was in a collection passed down from my grandfather who died in 1970's. Thanks. $\endgroup$ – Patrick Garrett Oct 25 '18 at 19:29
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    $\begingroup$ Have you cleaned the rock? If it was common, I'd say it could be hematite, pyrolusite, or black kyanite, with the latter two being less likely. Doesn't look rod-like enough to be hornblende or arfvedsonite to me. I wish you knew where it was found. Even knowing whether your grandfather found it himself and which places he visited to collect minerals would help. $\endgroup$ – person27 Oct 27 '18 at 22:03
  • $\begingroup$ Please add the missing information according to this guide. $\endgroup$ – gerrit Nov 2 '18 at 12:28