Description: There's no lack of candidates for the dark stuff - Hausmannite, Hematite, Jacobsite, Magnetite,... and the grains are small and aren't idiomorphic. I don't have a microprobe at home, and on these scales, I'm not very good at making scratches either. Time to walk over to the refrigerator and pick up one of those little magnets. Although it's a fairly weak one, it attaches itself to the side of the specimen with a firm clac. This rather narrows down the possibilities: Magnetite or its Mn analogue, Jacobsite. (Given what else is present on this specimen and given known assemblages according to the aforementioned book, Jacobsite is somewhat more likely.) Field of view 8.9x12.6mm.

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