hello! i found this a couple of weeks ago in a stream... my first thought was that it's a flint nodule but it's such a strange shape and texture that i'm tempted to think it might be a fossil? but i'm not sure what it could be apart from maybe an antler, or wood? there's no texture in the cross section but it is lighter towards the outside of the stone in some places in a rough, faint ring, which isn't obvious in the photos.
I'm certain its just a flint, not that it looks anything like one on the outside any more, i expect its been very eroded over many years out in the elements.
You can tell that this is a flint from the image no 0771 the chips around the outer part are a dead giveaway.
I agree with it being flint.
It's a bit of a head scratcher, though, as regards what (if anything) it represents.
It does have something of the look of antler, but it is very unlikely you'd find a fossil antler, and even less likely it would be composed of flint.
Wood, maybe. But no internal structure, But there again, ir could be a cast.
I wonder about it representing an Acroporid coral (staghorn coral). It is the only thing I can think of that is of the right shape and which might occur in a flint-chalk-forming environment. The surface texture is not necessarily right, and it is a shame it doesn't have any coralline internal structure - which could be explained if it was a cast (filling a void after the original was dissolved, for instance).
Some tabulate corals also have the right overall shape, eg. Thamnoporella
Both wood and coral are often petrified as silica. Curiously, however, both are often in the form of agate rather than flint or chert.
I note the vague banding you mention, but your specimen is not made of agate.
So, no closer to an answer; just thinking out loud.
A possibility is flint representing Thalassinoides burrows
The burrows are typically ramifying, eg.
Here are some in chalk, though not represented as flint
http://www.discoveringfossils.co.uk/hunstanton_fossils.htm (search for 'Thalassinoides')
And they are known to be represented as flint
It is just that your specimen looks somewhat different to most...