this is an example on the internet
Look enough on the internet kinds of things are possible.
Choice one. Google it.
Choice two. don't.
Are you here to argue your stone is something not agreed with here? Then go back to Goggle.
Have you done any work with flint?
Look up English flint Nodules on Google.
Bust the crust off just one round nodule and leave a round hammerstone. I'll applaud.
However by the time you manage to knock the crust off the nodlue or break a chunk off a largenodule andreduce it to a crude sphere... You'll realize how brittle flint is.
After all that work you would hammer with a piece of flint?
Just as a cutting tool needs to be harder than the material being cut ; so too a hammer needs to be more durable than what is being hammered.
Are flint hammers an actuality in Europe or are they a theory?
I'm imagining one eye users for a reason related to my breaking flint into flying shrapnel pieces while knapping. Using a gob of flint for a hammer might want a plaster (band-aid) on hand to patch with for other anatomy parts. And please keep fragments out of my tea and crumpets.