Gastrolith question

[Moozillion]

Amateur alert: i am NOT a professional paleontologist; I am a semi retired therapist who happens to be a paleontology hobbyist.

I've seen several things advertised as gastroliths, and the prices seem easily doable.

But HOW in the world is a rock determined to be a gastrolith, and not just a smoothish-rock that's a bit worn?

A rock that has been inside a prehistoric animal (not just dinosaurs, I'm guessing?) is WILDLY cool, but a smoothed and tumbled rock is not. 

 

[Randyw]

As far as I know the only sure way to tell is if the stones are found in the abdomen area of a skeleton and there aren’t any other stones like them in the surrounding matrix.....

[jpc]

I think if you are looking to buy a gastrolith, you are setting yourself up for bad results.  I can go the the local riverbed and pick up 1000 "gastroliths". 

 

I am a professional, and I do not trust any gastrolith unless it is found in close association with a gastrolith bearing beast.  I did find some obvious gastroliths in a plesiosaur prep job many years ago.  Fine shaley matrix, with a small clump of marble sized rounded pebbles and a few baby ichthyosaur vertebrae... stomach contents. 

 

Isolated gastrolith?...  I am skeptical.        

[grandpa]

I recall a trip in '94 to the Moab, Utah area hunting in an area known for "pigeon blood" agate that had no stream beds, nor ancient stream bed indications, etc.; the rocks in the area all had sharp, distinct edges.  Nonetheless, over the course of the day I found 3 - 4 very rounded, polished looking rocks that seemed quite out-of-place from all other surrounding material.  Knowing that this was also an area that reportedly had 'dino bone',  I declared these to be gastroliths and kept them.  Was I correct?  The scenario made sense to me at the time, but how would I ever really know?

One thing I do know for sure:  I'd never trust a vendor selling 'gastroliths'; they're too easy to fake.  I'd have to find them myself.

[jpc]

1 hour ago, grandpa said:

 

One thing I do know for sure:  I'd never trust a vendor selling 'gastroliths'; they're too easy to fake.  I'd have to find them myself.

Bingo!   

 

Yes, these that you talk about are the toughest to call.  I have also seen nice round smooth rocks in the Morrison Fm that could easily be called gastroliths.  I don't think you are wrong to call them so, but, personally, I would call them "possible gastroliths".  Some day we may come up a technology that can differentiate true gastroliths...  

[Tidgy's Dad]

I think smoothed and tumbled rocks can be pretty cool. 

But I would't pay money for one. 

[grandpa]

17 minutes ago, jpc said:

"possible gastroliths"

Excellent idea!  That's much better than what I'd relegated them to - "bucket in the backyard". 

[Moozillion]

9 hours ago, Randyw said:

As far as I know the only sure way to tell is if the stones are found in the abdomen area of a skeleton and there aren’t any other stones like them in the surrounding matrix.....

Thanks, Randyw- this certainly makes sense to me! 

[Moozillion]

8 hours ago, jpc said:

I think if you are looking to buy a gastrolith, you are setting yourself up for bad results.  I can go the the local riverbed and pick up 1000 "gastroliths". 

 

I am a professional, and I do not trust any gastrolith unless it is found in close association with a gastrolith bearing beast.  I did find some obvious gastroliths in a plesiosaur prep job many years ago.  Fine shaley matrix, with a small clump of marble sized rounded pebbles and a few baby ichthyosaur vertebrae... stomach contents. 

 

Isolated gastrolith?...  I am skeptical.        

Thanks, jpc! I was not looking for a gastrolith at all, was looking for other stuff, but saw an attractive price and thought I'd check it out. I can live quite happily without a gastrolith- and even MORE happily without a FAKE one! 

[Moozillion]

7 hours ago, grandpa said:

I recall a trip in '94 to the Moab, Utah area hunting in an area known for "pigeon blood" agate that had no stream beds, nor ancient stream bed indications, etc.; the rocks in the area all had sharp, distinct edges.  Nonetheless, over the course of the day I found 3 - 4 very rounded, polished looking rocks that seemed quite out-of-place from all other surrounding material.  Knowing that this was also an area that reportedly had 'dino bone',  I declared these to be gastroliths and kept them.  Was I correct?  The scenario made sense to me at the time, but how would I ever really know?

One thing I do know for sure:  I'd never trust a vendor selling 'gastroliths'; they're too easy to fake.  I'd have to find them myself.

Good to know! Thanks, grandpa! 

[Moozillion]

5 hours ago, Tidgy's Dad said:

I think smoothed and tumbled rocks can be pretty cool. 

But I would't pay money for one. 

Hi, Adam! I do agree on both counts!