my dog grabbed this joint bone out of a river in the woods in Devon, he dropped it behind me I turned to see it had some features that made it look like a bone i.e. a peforated chalky like exterior that appears like detoriated bone and at the bottom of the ecofact where the joint of a bone would connect to the rest of the bone there is what looks like a central core that could be bone marrow.
I thought it was just a run of the mill bone, but it has a flint interior, so I presume it must be a bit old. Also, it is quite a clean break on the bone, could this be done naturally of by people?
It is flint, and it just happens to have a somewhat bony shape.
Flint comes in nodular and tabular forms, both of which are knobbly, and all sorts of intermediate lumpinesses. As a result, many lumps of flint look, to the human eye, a bit like one thing or another.
The 'bone marrow' appearance is a manifestation of 'rotten flint'. It is usually due to the breakdown of earlier sponge fossil material.
Flint can also have a strange banding, again causing folks to think of some fossil connection - whereas it is a non-biological phenomenon.