What is this 3d puzzle ?

[Denis Arcand]

I found this yesterday,  it was very fragile and broken in many pieces when I handled it.

 

 

Edited September 13, 2022 by Denis Arcand

[Gramps]

Could it be a phosphate nodule in shale?

[Denis Arcand]

20 hours ago, Gramps said:

Could it be a phosphate nodule in shale?

 

It could be that.  I find it interesting that it has as a elevated rim around it.  it look like it's the same kind of rock inside and outside

 

I still have some interrogations, I'm not dismissing a nodule,  I'm just checking if a burrow is a possibility and how we differentiate a phosphate nodule from a small burrow ?

 

For my untrained eye the following burrow look similar to what I found 

 

 

but again, concretion and nodule also look similar, at least for me 

 

 

Edited September 13, 2022 by Denis Arcand