Rugose coral or nautiloid shell imprint?

[Alexthefossilfinder]

Here's a find from last summer. I originally classified this as a nautiloid, though I think it could be a horn coral too. Unfortunately I'm not very familiar with the inner workings of either and I can't see much that could point one way or another. I do think it's a nautiloid judging by how straight it is, but I would appreciate feedback from anyone with more experience.

[Ludwigia]

I'm afraid that this thing is too disturbed to tell one way or the other.

[Fossildude19]

Could also be a suggestively shaped vug in the rock.   

 

 

[debivort]

If I had to guess, I'd go with vug, based on the last picture.

[FossilDAWG]

I agree, it is not identifiable with any kind of a fossil and "vug" is the appropriate description.  It might have started out as something biological but it's too altered now to say for sure.

 

Don

[Tidgy's Dad]

Please don't use coins for scale. 

[jpc]

13 minutes ago, Tidgy's Dad said:

Please don't use coins for scale. 

This is a very international crowd and many folks have no idea how big a Canadian nickel might be. 

 

[Alexthefossilfinder]

7 hours ago, jpc said:

This is a very international crowd and many folks have no idea how big a Canadian nickel might be. 

 

Interesting, I never would of thought of that. What should I use instead?

[Tidgy's Dad]

1 hour ago, Alexthefossilfinder said:

Interesting, I never would of thought of that. What should I use instead?

How terribly parochial. 

How about a ruler? 

[Coco]

Hi,

 

What means "vug" ? (International forum...).

 

Coco

[Mahnmut]

Vug: "a small cavity in a rock or vein, usually lined with crystals"

I do not know if its a complete synonym of druse, or if there are differences in detail.

Best Regards,

J

[debivort]

2 hours ago, Mahnmut said:

I do not know if its a complete synonym of druse, or if there are differences in detail.

Druse (drusy) crystals are a coating of small crystal points. They could be on the inside or outside of a surface. Vug is the cavity. So in this case, there appears to be a drusy lining of the vug. 

 

A vug can sometimes form when a crystal in matrix dissolves out leaving a crystal-shaped cavity.