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Fossil ID: pyritized wood, mica, something else?


Lisa-wri

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Hi there,

I found this specimen on a hike outside of Denver, Colorado. It was laying in the middle of the trail. It’s about 10cm long. It has grain that looks like wood or layers like mica. It’s also gold and shiny like pyrite or mica. It’s layers are wavy and it leaves a gold dust behind when handled. It’s stunning when the light hits it. Hoping to identify what it is.

 

Thank you!

Lisa

 

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E357B042-5F4B-4462-B974-7E5D866A6B0B.jpeg

0F272EB1-A222-40D3-8DDC-1878FA7E870F.jpeg

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Bradley Flynn

Hi That is a really nice piece. I have a similar specimen that was identified as schist, search schist on the webs and see if it matches any of the various forms. I'm in no way an expert, so please don't take my word for it :rolleyes:

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I think you’re both right. I found a detail shot of a mica schist and it has the same wavy/ridged surface pattern. And it definitely flakes like mica. 
 

Thank you so much!

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There is a lot of pyrite in the mountains around Denver but it would be almost unheard of to find a 10 cm piece lying on the ground unless it was just mined and dropped- besides that, exposed pyrite rusts.

 

one additional clue to sort the two- pyrite is very dense- it will feel heavy for it's size

it is twice the density of mica

 

 

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The weight feels as I would expect it to, not too heavy. So I believe it’s likely mica. I didn’t know that about pyrite... that it rusted or that it’s more dense. Thanks for the insights!

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