Hey Alex (@alex-rosas), I see what you are talking about and this kind of structure can easily be misinterpreted as fossil, but it seems to me that it is just a mineral structure (lacquer or coating) from iron oxide (probably pyrite) or marcasite. I have seen lot of these structures but most of the time it was just from mineral origin. Sometimes real organic material (like tree leaves) attract such minerals so that the minerals get accumulated in the organic structure and replace it. But then you still should see the leaf structure like venation etc. But like I said earlier, such examples are a very good way to understand how complex this field is and how much we have to take a closer look until we can state: yeah this is fossil!
Thank you for sharing it!
All the best
Ronny
btw: thank you for the congrats 🙂