Is this a fossil or a rock?

[Shiva]

Is this a fossil? Found at mornington peninsula, Vic Aus on a beach.

Cheers!

[Ludwigia]

No. It's a rock.

[Rockwood]

3 hours ago, Ludwigia said:

No. It's a rock.

Too far.

It's hard to say it isn't a rock. It could be a fragment of thick shell that is nearly indistinguishable from a rock however.

The holes appear to be biological in nature. Made by boring organisms. The time period when they were made would determine whether they can be considered trace fossils or not. 

[supertramp]

I was thinking of weathered boring sponges traces too.

Edited October 31, 2021 by supertramp

[Ludwigia]

Ok. So it could be a rock with weathered boring sponge traces.

[Shiva]

11 hours ago, Rockwood said:

Too far.

It's hard to say it isn't a rock. It could be a fragment of thick shell that is nearly indistinguishable from a rock however.

The holes appear to be biological in nature. Made by boring organisms. The time period when they were made would determine whether they can be considered trace fossils or not. 

I found it at a beach that is in the tertiary period, thank you for the informed answers, it helps a lot