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can anyone identify this strange rock found in Derbyshire, England?

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alt textThe rock was in a river, it has striations that don't seem to make sense. It is heavy, can be scratched with a knife and a very fine brown/black powdery grains can be scraped off. It doesn't fizz with vinegar. Has anybody got any ideas?

asked Nov 6, 2014 by riorita (200 points)

3 Answers

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Cool rock. It appears to have been polished by the water and sand of the river. The rock or material you scrape away is brown/black. Does it come off in flakes or grains? The beige colored substance between the striations is another softer material than the host rock.

answered Nov 9, 2014 by Weasel (58,980 points)
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Hi Weasel - thanks for answering. The stuff that scrapes off is very fine grains, it is very hard so I didn't get much off. It is a bit heavier and harder than I think it appears. I am confused the way the beige striations go both ways, rather than in layers. I haven't seen that before.

answered Nov 9, 2014 by riorita (200 points)
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Think of it this way, one rock forms and water containing minerals seeps in and solidifies filling all the crevices or striations with a different mineral. Agates, for instance, having copper inclusions, or granite having quartz veins...in the second case there is little rhyme or reason to the haphazard formations.

answered Nov 10, 2014 by Weasel (58,980 points)

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