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I was out in Swinley Forest in Bracknell(United Kingdom) last weekend. The area is a large pine forest but the ground is full of flint and is very sandy.

I stumbled across a piece of flint and noticed that there were some very interesting marks on it. Flint rock with potential fossil.

As you can see on the right edge of the rock there is an indentation with some vertical lines and some circular patterning. I've included a zoomed in image below.

My question is whether this could be plant fossil or even part of the fin of a fish with scales attached.

Many thanks!

Zoomed in image of Flint rock with potential fossil

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Assuming that the identification of the rock as Flint/Chert and not Limestone/Dolomite is correct I'd say it's a formation artifact rather than a fossil. What I mean is that at some point as it was forming, flint can form in two ways one is due to silica saturated water acting on limestone and the other is by direct precipitation from mineral saturated water in shallow environments, the small bead-like structures were created within or on the surface of the rock. It may be a surface impression from a fossil that was once part of a larger piece but as it is now there's no evidence of a material difference between "fossil" and the country rock of the flint. This opinion is coloured by the fact that here in New Zealand fossils in our flint are vanishingly rare, I'm not sure if that holds in England though.

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  • $\begingroup$ I tend to agree that this is an impression of a fossil and not actually a fossil. I would also add that I've seen gastropods in chert, in the Mishash formation in Israel so it is occurring. $\endgroup$ – Gimelist May 9 '18 at 4:24
  • $\begingroup$ @Michael We get those too but they're so rare that the Earth Science department at our local University has a cash bounty for anyone willing to donate one to their collection because in over a hundred years they've never found one during departmental fieldwork. $\endgroup$ – Ash May 9 '18 at 14:36
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    $\begingroup$ Technically a natural mold of a body part is still a fossil What Ash is saying is that it is possibly is a chemical/depositional artifact not a fossil. $\endgroup$ – John May 9 '18 at 21:27
  • $\begingroup$ All extremely interesting, thank you for your help guys! $\endgroup$ – robertmegone May 11 '18 at 6:54
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Your best bet with something like this is find the nearest museum and bring it in, they will be familiar with the local geological artifacts. From just the photos it is hard to check for all the marks we would expect from a natural mold. As Ash said there is a chance it is just a pseudofossil but without being able to see all the internal surfaces I do not feel confident saying for sure.

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  • $\begingroup$ Many thanks! I'll see if I can find somewhere to take it. $\endgroup$ – robertmegone May 11 '18 at 6:54

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