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found several dozen fossils like the one below on Debordieu Beach (~20mi south of Myrtle Beach, SC): can anyone help to identify?  They are black, wafer-thin discs, roughly 1 in (2.5cm) in diameter, with a ripples-in-water pattern of concentric circles.  Any help with an ID would be most appreciated--thank you!

Front View.jpg

Side View.jpg

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Welcome to the Forum! :)

Can we see other examples of your finds similar to the one you've posted?

Also, it would be good to see them from different sides (front/back/lateral).

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That is really interesting! But I also have no idea as yet :headscratch:

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I bet they are phosphate nodules with overactive imaginations.

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Brett Breakin' Rocks
18 minutes ago, PaleoNoel said:

It almost looks like an odd ray dermal denticle or some type other strange fishy piece.

They have bee found before, I linked a post.

 

You know .. I saw this when it was posted and first thought it was Geologic or something like a Beekite ? But there was not a consensus in the post noted. I'm not a beekite preservation expert but that was my first impression, at least the shape is similar (but the concentric circular shapes are so sharp and distinct which does not look like a beekite). Maybe, as mentioned in the post by Ynot, they could be slag ? 

 

 

Cheers,

Brett

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Looks like we're still lacking a reading on hardness.

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Brett Breakin' Rocks
4 minutes ago, Rockwood said:

Looks like we're still lacking a reading on hardness.

Yeah ... curious if it leaves a streak. It also looks rather brittle. 

 

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57 minutes ago, Rockwood said:

Looks like we're still lacking a reading on hardness.

Thanks so much for the input thus far.  I'm sorry to say that I'm away from the vacation house where I found these, so I can't respond definitively on the hardness question until I get back there to test.  

 

Anecdotally, I can tell you that the pieces are quite thin and somewhat brittle (you could break a piece in half with two hands, using roughly the force required to break a pencil).  That said, the surface is quite hard: it wouldn't show any scratching from a fingernail, and would be more likely to flake in small pieces than to scratch under a sharp metal point.  In the original photo, you can see where small portions of the black surface in the lower-right quadrant have chipped away, revealing a whitish substance underneath similar to quartz (crystalline, powdery, etc).  This white interior is more evident in some of the pieces from the 7/17/19 post. 

 

That earlier post reflects a nearly identical set to the specimens I've found over the past year: 40+ pieces, averaging roughly the size and thickness of an Oreo cookie wafer.  Some appear to have a single central point of origin for the concentric circles, while others look like a puddle rippling from several different stones thrown at once.  They have a musical/glassy sound when they knock against one another. 

 

I've added an additional photo, which shows an angled view of the piece that gives a better sense of the whitish interior and texture.  

Lateral view.JPG

Edited by megaman
Adding a photo
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I think, all of the specimens from the two post are geoligical formations.

My first thought was phosphatised beekite, but I have no proof for that.

It was just an idea.:)

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I suspect you will find this stuff will burn if given enough flame...I have seen something similar before, many many years ago in that area. I'll reserve my hypothesis in lieu of some testing.

 

Will need a flame test, a streak test, and perhaps a nail polish remover overnight soak test on a small chip to be sure.

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  • 2 months later...

I have seen chunks of this (white/gray rather than black) that pretty clearly peeled/flaked off the inside of a mollusk shell, for what it's worth - and some specimens that were supposedly collected from the Lee Creek Mine.

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I'm finally back with the specimens (found several more on the beach today), and I was able to confirm a few points:

  1. They are not flammable.  I exposed a few thin edges to a lighter flame for 30+ seconds, with no evidence of ignition or substantial burn marks.  The specimens did get extremely hot (could not be held), but were otherwise unaffected.
  2. They do not scratch easily.  I attempted to scratch the surface of several pieces with a stainless steel, which left no blemishes.  The pieces do scratch stainless steel quite easily, and drop-forged steel with some pressure, so I'm assuming a Mohs hardness of at least 6 (I currently don't have access to hardness picks).
  3. They are brittle.  A few pieces are very solid (1/4" wide), but most are 1/8" or less and can be broken between your fingers with the same force required to snap a pencil.
  4. The concentric circles vary on each side/between layers.  I've included two images of the same specimen, flipped 180 degrees on the horizontal axis.  On side A, the concentric circles emanate from two points (one near the center, the other on the left).  On side B, there are three distinct points of emanation (one in the middle, and one on either side).
  5. The interior of each piece is bright white.  A cross-section of each piece (or when the layers break unevenly) reveals a very different composition: crystalline, powdery, and sparkling--almost like sugar.  This chalky-white material can be seen in several of the pieces in the attached "Group" photo.

I'm eager to hear any other thoughts or tests that might be conducted to help with identification!

Fossils Group.jpg

Fossil Side A.JPG

Fossil Side B.JPG

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ScottBlooded

Just want to say, your finds here are really cool and wanted to bump this (perhaps unnecessarily) because these kinds of posts (mystery, no immediate consensus from experts) are my favorite kinds of posts on here. A lot of times I can dig around and land in the general ballpark (very general, I’m an amateur) but I have legit no idea and don’t want to see this drift away without a concrete answer.

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hemipristis

I have to say I’m stumped.

Have you tried HCl or vinegar to test for carbonate

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While searching I came across a process for coating metals with black oxide. Suppose these could be scraps from an industrial process ?

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LabRatKing

What color, if any, the the flame become from that test? Does the crystalline interior flame different from the exterior?

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On 1/17/2021 at 1:34 PM, Boesse said:

I have seen chunks of this (white/gray rather than black) that pretty clearly peeled/flaked off the inside of a mollusk shell, for what it's worth - and some specimens that were supposedly collected from the Lee Creek Mine.

Phosphatized Mclellania? I could see the aragonitic shell dissolved away and then the enigmatic Mclellania phosphatizing in a lag. Maybe not 3D enough though. Was the beach recently renourished? Am assuming the flat ones don't bend at all.

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YES, that's what I remember seeing! Don I bet you're right. Here's Mclellania from the Lee Creek I volume. Pay attention to the lower right:

 

image.thumb.png.085a4f5dece554b3201470f316610849.png

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if it's a fossil this is as good a guess as any.

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abyssunder

Harder than Duracell... :default_rofl:

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