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Bands in black schist
  
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Kara




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PostPosted: Nov 07, 2018 03:50    Post subject: Bands in black schist  

I am thinking this must be a black schist, a metamorphosed black shale. It makes black greasy stains when touched and I think it is due to high graphite concentration - I have washed it a thousand times and still it is different from mica schists, greasy. Graphite is common here and black schists also, but this is the first banded schist I have found. There is a vein of quartz and feldspar in it, and some staurolites.

I am wondering what produces these black bands. I know graphite can be silver-grey or black depending on the grain/ flake size and type, but is it the answer here? If you know better, please help. From Finland.

Thank you! Kara



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pic taken with a camera flash: the mica shine makes the rock look more pale than it is.
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Pete Modreski
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PostPosted: Nov 07, 2018 11:54    Post subject: Re: Bands in black schist  

Yes, I would guess that it's graphite/graphitic schist in those bands.
Are those staurolite crystals, in the first photo?
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Kara




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PostPosted: Nov 07, 2018 12:25    Post subject: Re: Bands in black schist  

Thank you Pete. Yes I think they are staurolites, at least they look like them - haven't done any tests.
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