Portsmouth RI beach.. Fossil? Rock?

[Emily1]

Hello!

I found this piece in Portsmouth RI this weekend on a shale beach (picture attached). I'm just not sure what the shale is attached to--- it *looks* like a piece of bone, but I've been doing some image searches and cant find anything really similar. Sorry for my hand in one- I couldn't get a clear shot of the edge otherwise.

Thanks so much in advance - I appreciate any insights into what this might be!

Emily

 

 

 

 

[Tidgy's Dad]

Igneous rock with a calcite layer formed where there was a break?  

[Emily1]

I'm fairly certain the black is wave-worn shale, which is sedimentary. The beach was full of it. And I'm not an expert on calcite, but I've never seen any that formed like that. It has a porous, kind of fibrous texture, but it's definitely rock. Thanks for taking a look!

Edited August 18, 2021 by Emily1
clarifying adjectives

[Tidgy's Dad]

It could be shale, though it's a bit blobby in places and I see no bedding planes. 

But the fibrous calcite resembles what we used to call calcite beef back in the UK. It used to be found in shales on the Dorset coast, now I come to think of it. 

[Fossildude19]

If you drip some vinegar on the white parts, does it fizz? 

If so, then it is calcite. 

Not seeing anything really fossil-ish there, though. 

[Emily1]

Thanks so much for the help! It's really great that you all are willing to share your knowledge and experience.

[Pagurus]

I don't have a source link handy, but with your description of a fibrous texture I think it may be an unusual mineral or rock known as fibrous muscovite-chlorite found in the area. I have found some at the Corys Lane beach site. This is a piece I found:

 

I'll try to find a link with more information. 

 

Here's one link, and here's another

 

That's just my opinion, from a photograph, of course. It's at least a possibility to consider.

Edited August 20, 2021 by Pagurus

[hemipristis]

The fibrous material is serpentine, a monomineralic metamorphic rock., variety chrysotile.  When chrysotile gets really hairy (yours isn't), it's asbestiform (i.e., asbestos).

 

The massive portion of your specimen:  can you dig into it with your fingernail?  If so, it is talc (could be soapstone). Talc is frequently found associated with serpentine

 

There are a few outcrops of soapstone/serprntine in RI that are archaeological sites. You can see bowl-shaped depressions where the material was carved out by Native Americans and turned to bowls.  This was in the Archaic cultural period, before they learned to make pottery

On 8/19/2021 at 6:36 AM, Fossildude19 said:

If you drip some vinegar on the white parts, does it fizz? 

If so, then it is calcite. 

Not seeing anything really fossil-ish there, though. 

the white mineral is probably magnesite (magnesium carbonate), a very common accessory mineral in serpentine bodies

Edited August 20, 2021 by hemipristis

[Emily1]

Yes, I can leave a faint scratch with my fingernail, can't dig into it though. We tried the vinegar, but saw no fizz on the white part. Too bad, we liked the idea of 'calcite beef' ☺

It was from the Corys Lane beach site - small world! It is duller than the piece Pagarus posted, though. 

I have an aquaintance in the geology dept at Uconn. Now that I know it's not a fossil, I'll probably show it to him at some point to get an in person opinion. Again, I'm so appreciative that you've all taken the time to look at it. Thank you!