What rock?

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Offline jatufin

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What rock?
« on: 12/03/2012 20:23:59 »
Ok, this IS a homework. "Go out, pick a rock and tell what it is."

I took a stone from riverbank, whacked it in half and went back home. And now I feel like total idiot, cause I can't identify this simple piece. Medium grained, anhedral, no foliation, scrapes glass, seems like igneous to me and I'm leaning to diabase (dolerite), but there's no finer matrix whatever. Andesite?   :o

For the homework I'll pick a nice piece of granite even a looser like me can identify. But please tell what this is, and how do you know?  :-'(


Offline Atomic-S

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Re: What rock?
« Reply #1 on: 14/03/2012 04:56:44 »
Sometimes people bring rocks to me that are as clearly defined as what you have, and I have to tell them, that to me it is a "leaverite" -- of no interest and you can leave 'er right where you found her.


Offline Sprool

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Re: What rock?
« Reply #2 on: 15/03/2012 15:28:52 »
looks to me like a small disc of some type of copper alloy?


Offline Bass

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Re: What rock?
« Reply #3 on: 20/03/2012 16:55:21 »
can you see any crystals in the matrix?  I couldn't tell from the photo.
If not, I would guess fine-grained quartzite.  If igneous, the light color suggests rhyolite-dacite rather than andesite.
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