Beak like formation on rock is fossil ?

[Piantadino]

Hello. I am just a novice interested in rocks. I have a couple of rocks I picked up from the mouth of the Bega River (not sure what they are: aphanitic, heavy, slightly magnetic and brown). They both show a strange formation as in the picture: a small split diamond shape enclosed by an oblong beak like dome. The rocks have no other accidents. Is this a fossil or a crystal formation of some kind?

Roderico

 

[benmick6]

it looks like a type of limpet type shellfish we get here
ben

 

[Colin&Lee]

Yep, that's a Barnacle or Limpet

Cheers

C&L

 

[Piantadino]

Ok thank you - I will follow on your hints.
Cheers