drilled or not?

[nunyabiz111]

rock is of a rather hard, dense and heavy composition. i haven't yet 'reamed out' or even thoroughly cleaned the it other than rubbing it barehanded under running water:

video showing rock from all facets:

 

[rginn]

I think it's just natural erosion. I don't know what that would be used for.

 

[Treasure_Hunter]

Natural, most likely fossil fell out.

 

[nunyabiz111]

Natural, most likely fossil fell out.

sounds quite legit

 

[Tdog]

I think softer material, possibly Crinoid fossils, eroded out leaving the voids.

 

[Treasure_Hunter]

I think softer material, possibly Crinoid fossils, eroded out leaving the voids.

TDog is most likely correct on the crinoid fossils.