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Corolla NC beach. Fossil or rock?


Katherinez

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Found this today on the beach in Corolla NC. Fossil? Rock? As always, I am intrigued!

Photo_2019-08-10_08-13-06_PM.png

Edited by Katherinez
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I am trying to learn here... Why would it have two different types of "layers." One looks like bone and the other is harder and shinier.  I assume this happened in the ocean... I am interested in possible age and how the whole thing came about.

 

Thank you!

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3 hours ago, Pemphix said:

water worn rock...

Yes, it is water-worn. The action of water brought out the two different materials within this piece rather nicely. In other words, this pieces consist of two (somewhat) different rocks.

 

1 hour ago, Jackson g said:

probably an ironstone concretion.

This does not scream ironstone concretion to me. It appears to hard, to glossy, at least to me. Can you scratch the glossy part with a knife blade?

 

20 minutes ago, Katherinez said:

Why would it have two different types of "layers."

Its a water-worn piece of a layered rock sequence. But it is very hard to tell, which rock are really involved in this piece.

The glossy part looks like some dense, quartz-rich material (either quartzite, chert, but I can also not exclude vein quartz).

The porous part could be a weathered sandstone, the pits probably resulting from dissolution of feldspars or carbonates. But it can be also some kind of schist or even highly weathered gneiss.

So, I am not even sure, if your piece consists of sedimentary rocks or metamorphic rocks. What is usually found in your area?

 

A little bit strange is the dark color. In my area, I have found smooth, nearly black quartz pebbles up to 20 cm across. The black colour is only a very thin surface coating and the pebbles where found in a slow-flowing, small creek and are reworked from older sediment. The coloration comes from lying in the creek. Did you find your piece in a quiet area of the beach, maybe even above the high-water-mark? Would you mind snapping of a small piece of the glossy part?

 

33 minutes ago, Katherinez said:

interested in possible age

Maybe we are able to say something about that, if we know what it really is and if we also know the regional geology.

 

Franz Bernhard

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