Hi, I found this unusual piece of flint amongst some flint gravel in my garden. It's tooth/claw shaped and has some unusual markings on it. I would be extremely grateful if you could please let me know what it may be?
I am pretty sure that it is not a fossil, it looks like a piece of chert (fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock), which is flint of sorts. Many pieces of chert or flint resemble fossil shapes and forms but this is just coincidental and they are therefore classified as pseudofossils.
Often with pseudofossils, it is the overall shape that leads to misinterpretation. With this specimen the shape is not that remarkable. But there is a patterning that raises one's curiosity. While some flints are casts of burrows (often said to be shrimp burrows), others can include smaller burrows, and I suspect that may be what we are seeing in this specimen.
Another possible explanation is siliceous coprolite, with the patterning being due to food pellets/remains; less likely, I feel.
There is a lot of guesswork with flint and chert, giving rise to such resources a the 'chert formation' and 'flint formation' sections in this web page