Canada Bay of Fundy / What is it?

[Jessi]

 

 

 

 

 

[Rockwood]

Phosphate nodule?

[val horn]

It is very pretty but not a fossil.  Not sure what kind of fossil would survive those kind of tides

[Rockwood]

8 minutes ago, val horn said:

It is very pretty but not a fossil.  Not sure what kind of fossil would survive those kind of tides

Actually, the bay is a hot spot for all sorts of fossils. Many probably do get redeposited by the tides.

[palo69]

Looks like Septaria. One of the types of crypto-crystaline nodules in sedimentary rocks, with cracks or veins inside. On a chip or cut, they often have unique often picturesque design. They are often mineralized, and contain various minerals inside.

[Ludwigia]

This is definitely NOT a septarian nodule, although I'm in turn not at all sure what it is. It does however look somewhat like a piece of soapstone which someone was scratching away at, but that's just an uneducated guess.

[Jessi]

To add some info: it was found within the tide of that day (last Tuesday) and it is not soap stone. I used a serrated knife to try and saw a small line in it but it is pretty solid and only resulted in minor scratches on the rock surface. Maybe I shouldn’t have done that but I’m dying to figure out what it is. 

[Jessi]

I don’t know a lot about fossils and rocks, but here are a few theories from me and my family.

We wonder if this is sedimentary rock and the lines are some kind of aquatic plant?

Or second theory: there is a saltwater clam out there called the “wrinkled rock borer” that is capable of  boring itself into rocks.

Or third theory: used to be sediment at the bottom of the ocean and the lines are marine life trails?

 

Obviously, I’d be more thrilled if it was something rare and wonderful, but I am willing to accept that an Artistic clam somewhere made this.

 

Thanks to everyone who responded so far.

[Rockwood]

I think it more likely that the lighter color is the look of the material when it is weathered. Oxidation and hydration are two common forms of weathering. The coating of weathered material has been eroded away from most of the surface. 

[Jessi]

So the weathered parts, being a depression  didn’t get polished like the rest of the darker surface?

what could have etched the rock like this?

[Rockwood]

Yes. I think it's just the original shape. Nodules / concretions form in unconsolidated sediment as molecular forces attract mobile minerals to a nucleation point. The bay is known for its fossilized trackways so there apparently were mud flats around in the Carboniferous period.  It could also be result of abrasion on a roughly fractured piece. 

[Jessi]

Rockwood: So maybe fossilized trackways or maybe just it’s natural form. Is there any way of getting more information on this piece that you know of? 

[Rockwood]

8 minutes ago, Jessi said:

So maybe fossilized trackways

No. Trackways and nodules form in similar environments.

You could try a streak test to determine what it's made of. Draw it across a piece of unglazed porcelain and report the color of the streak. It won't mean much to me, but we have geologist who could chime in.