Jed, this is probably a dumb question, and it's probably just shale (or something I don't know), but does it have even a weak magnetism to it? Do you think if you roasted the stone in a camp fire, it would be magnetic? I probably just have iron ore on the brain and if so, I hope someone comes forward to correct me.
I've sent you some photos, via PM of a mineral someone posted to the little Iron Smelters group I belong to on Facebook, I can't post it here, because I really don't want to post someone else's photos in public without their permission, but they called the mineral siderite (iron carbonate). I thought siderite was crystalline in form, like large crystals, but the photos shows more worn, sedimentary rock like you've got. I thinking (more hoping) you might have an impure, shale-ish version of that. It's lack of plasticity and extremely small shrink rate would support this, I think, maybe. Possibly. At the very least, it's not all shale.
It looks very much like your pictures. So it may have Mg in it. That would explain the low shrinkage. I will try roasting some of the rock. I do know that if I heat it up with a torch, it pops and explodes a little bit. Nothing happens once it is milled.
Roberta, my geology searching also mentioned Pierre shale. I have two buckets of the granite as well. It melts to a beautiful white.
jrgpotsMember Since 15 Mar 2013
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