Found on the beach in my hometown (Charleston, SC) a few months ago-

[DoubleD843]

Upon first glance I was thinking potentially trilobite related, however trilobite’s caudal region typically tapers down/smaller. Secondly- I noticed that the gray striations area of the fossil seemed to have once been completely intact circumferentially around the black porous portion. Needless to say- I am stumped! 

[Tidgy's Dad]

Looks like metal to me?

[Kane]

I can at least guarantee this is not a trilobite. 

[johnnyvaldez7.jv]

@Tidgy's Dad

Could it be a vintage rotary/grinder bit?

[Tidgy's Dad]

3 minutes ago, johnnyvaldez7.jv said:

@Tidgy's Dad

Could it be a vintage rotary/grinder bit?

I don't know what that would look like, I'm afraid.

[johnnyvaldez7.jv]

@Tidgy's Dad

Sorry about that. 

Here is a variety of grinding stones.  I've found a couple that seemed to look like the subject piece in an area where building structures are pretty old. 

[Tidgy's Dad]

4 minutes ago, johnnyvaldez7.jv said:

 

Here is a variety of grinding stones.  I've found a couple that seemed to look like the subject piece in an area where building structures are pretty old. 

 

Maybe. 

Certainly more like that than any fossil I can think of at the moment.

[johnnyvaldez7.jv]

@Balance

I think you've shown photos of you working around tools... recognize this subject piece as a tool? I'm not familiar with any fossils other than Pleistocene material... so I definitely don't recognize it if it is a fossil... other than a first impression as a bit. Grinding bits/disc can break and or shatter when they are worn down.

Edited January 25 by johnnyvaldez7.jv

[Balance]

@johnnyvaldez7.jv I think it’s a bolt and nut. What left of it after eroding. 
 

I say that because it appears you have threads on the inside of the nut and what’s left of the bolt. The head of the bolt is gone. It would have been on the opposite end and most likely the shaft of this piece went through something. Like a board. 

 

??

 

Jp

 

Edit: Dang it ,Johnny. Now I’m thinking about this thing. I need to be getting my work flow started but instead I’m thinking a nut won’t be threaded past the surface. So if it was a nut it wouldn’t have threading on the broken face. 
 

So scratch this idea. 
 

Brain is currently computing photographic recognition program. Will report back when finished. 😂
 

Edited January 25 by Balance

[johnnyvaldez7.jv]

@DoubleD843 Are you able to test if this is magnetic?

[johnnyvaldez7.jv]

Maybe slag or porcelain?

[automech]

How about a measurement and pictures of the ends? I've used grinding stones in the past for engine work. And, the dark center "shaft" is slightly bent. Until the OP gets back with your question @johnnyvaldez7.jv, I don't think it's metal.

[DoubleD843]

I am visiting fam out west till next week- once I am home I will definitely snap a few more detailed pics w/ measurements, slap this thing next to a magnet and report back! 

[Al Dente]

3 hours ago, DoubleD843 said:

I am visiting fam out west till next week- once I am home I will definitely snap a few more detailed pics w/ measurements, slap this thing next to a magnet and report back! 

Another test would be to put a drop of vinegar on the layered part to see if it fizzes. That would indicate whether it is calcitic or not. I think this looks like it could be fossil. The dark rod shaped part could be phosphatic burrow fill from something that bored through a calcitic shell.

[DoubleD843]

10 hours ago, Al Dente said:

Another test would be to put a drop of vinegar on the layered part to see if it fizzes. That would indicate whether it is calcitic or not. I think this looks like it could be fossil. The dark rod shaped part could be phosphatic burrow fill from something that bored through a calcitic shell.

I will do this test as well! Thank you for the advice!!! 

[Mahnmut]

Hi,

although this could be a deformed part of a tool, my first guess would be fossil.

To me it looks as if the dark part was a  steinkern, meaning an infill of a former cavity,  while the layered grey end is what remains of the structure proper, maybe something crinoid-related?

Testing for metal (density, magnetic properties) could still be worth a try. The corroded remnants of a battery or related part (coal electrode in metal casing?) does also come to mind.