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BIF chert-something problem
  
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Kara




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PostPosted: Oct 08, 2018 10:13    Post subject: BIF chert-something problem  

Hello dear pros again! What would you name these two reddish coloured rock-types I now and then find in Finland? Both seem to have the same type of (microcrystalline?) (quartz?) matrix. Both have quartz hardness.

Could the first type with layered banding be somekind of sedimentary BIF? Are there other possibilities? The second type is somekind of rhyolite?

Thank You for help! Kara



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dontgogreen




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PostPosted: Oct 09, 2018 08:23    Post subject: Re: BIF chert-something problem  

Hello Kara,

If you are trying to make an ID of a potential BIF-type rock, knowing the geology of the area would go a long way. For instance, are these rocks part of a sedimentary sequence in an ancient ocean basin? Perhaps if you supply a location we can investigate further.
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Kara




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PostPosted: Oct 09, 2018 09:26    Post subject: Re: BIF chert-something problem  

These are found from Finland Ostrobothnia area near the Baltic sea. I keep finding these from glaciofluvial deposits. They are always rounded so they might have travelled a long distance.
In Mel'nicks book Precambrian Banded-Iron-Formations is written, that BIF are known in three different zones on the Baltic shield. The Finnish BIF:s I have seen in pictures are very different looking than this.



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marco campos-venuti




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PostPosted: Oct 09, 2018 10:21    Post subject: Re: BIF chert-something problem  

Absolutely no BIF. It looks more as a rhyolitic lava flow.
The other is a granite.
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Kara




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PostPosted: Oct 09, 2018 20:34    Post subject: Re: BIF chert-something problem  

Thank you very much for identification.
Kara



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