Americaspis americana - Is it Real?

[historianmichael]

I recently purchased this piece from a fossil dealer. It has a complete head shield of Americaspis americana and two partial head shields. Based on the information I could gather, my guess is that it was originally part of an old collection; however, since the piece had been with the dealer for a long time, they could not confirm how they acquired it. The information card I received with the fossil states that it is from the Wills Creek Formation in Perry County, Pennsylvania. I understand that to be the location of the now-closed site where you could find head shields of Americaspis americana. When I received the piece today, some suspicions arose, which may or may not be justified. I was hoping @fossilcrazy @traveltip1 or someone else with familiarity with Americaspis americana could help resolve some of my concerns.

 

My concerns are two-fold:

(1) The head shields have been painted with a brown paint. It is possible that the original owner did this to contrast the head shields with the surrounding matrix. The paint alone is thus not a reason to say that this is fake. What is weird though is that in areas where paint has been removed, there seems to be a strange bluish color beneath it. You can see that in some of the partial head shields.

(2) On one of the ends of the piece there is an edge that appears to have been cut by a saw and a portion that was left natural. There is a contrast in color again between these two surfaces. What am I to make of this?

 

I saw a piece on another auction site that looks very similar to my piece. Is it possible that someone faked a number of Americaspis pieces and they are now floating around?

 

The Piece

 

The Head Shields

  

 

The Suspicious End

[jpc]

This is a tough one.  In any case, I would not call it a fake, but a cast.  But if it was sold as a real fossil, then if it is a cast, then there is a problem. 

[historianmichael]

@jpc I may have been too quick to call it a fake. It was sold to me as a real fossil, so you are right that there would be an issue if it is a cast.

[Fossildude19]

The bluish cast is sometimes common in armored fishes - I think the ones coming from the Ukraine show this, from time to time. 

I think it is the color of the preserved bones in some cases. 

 

As far as the odd end - can you hold a match or lighter to it to see what it does? 

I know cut rock edges sometimes can pick up coloring more easily from different things than natural breaks.

[Misha]

11 minutes ago, Fossildude19 said:

I think it is the color of the preserved bones in some cases. 

 

I know this is a bit off topic but, do you know what causes this?

I've been wondering about that because Ukrainian fish, Catskill Fm. fish and others all show this blueish hue to them and it's quite interesting.

[Fossildude19]

@Misha

 

Could be de-phosphatization. Honestly, it is beyond my understanding.    

 

I found this in a PDF concerning Taphonomy of the East Berlin Formation in Connecticut.: 

 

"The mechanism of carbonate preservation of fish can therefore be explained by the metaphorical ‘switch’ to environmental contexts that no longer favor calcium phosphate precipitation (i.e. increased pH, reduced dissolved phosphate, increased magnesium etc.). The blue and white coloration of this type of preservation within Westfield fossils has led some to believe that the preservational mineral is in fact vivianite, an iron phosphate often associated with the digenetic alteration of apatite in iron rich sediments (McDonald and Letourneau, 1989). However, the mixed coloration might be explained by ionizing radiation of typical white carbonate minerals by urananite. Exposure of white calcite to x-ray radiation in experimental conditions is known to shift its atomic absorption spectra to mimic that of naturally blue calcite and give the transformed mineral a light blue hue (Calderon, 1983)."

[historianmichael]

@Fossildude19 I held a match up to the odd end for a few seconds and I was able to darken it. The spot came off fairly easily though when scrubbed with the abrasive end of a household sponge. Beside the dark spot, it didn't otherwise melt or something similar to that.

 

 

[FossilDAWG]

Can you find an unobtrusive spot where the fish seem to go into the matrix and try to remove a flake of matrix?  If the fish continue into the rock the specimen can't be a cast.  Also, are you certain about the brown paint?  People used to coat fossils like this with shellac, which can darken with age.  The blue color is a good sign as this is a common feature of Paleozoic bone fossils, but it wouldn't be easy to fake, nor do I think most people would bother.

 

Don

[LabRatKing]

3 hours ago, historianmichael said:

@Fossildude19 I held a match up to the odd end for a few seconds and I was able to darken it. The spot came off fairly easily though when scrubbed with the abrasive end of a household sponge. Beside the dark spot, it didn't otherwise melt or something similar to that.

 

 

That’s a good sign. That end has just been sawed. The most recent angle makes it clear.

 

I missed this earlier, but looks legit to me. No air but bibles or over uniformity of the matrix, etc etc etc

[historianmichael]

@FossilDAWG 

Unfortunately they are pretty well exposed already. I cannot seem to find a spot with more matrix around the head shields. I was able to flake off a small piece of loose matrix on the reverse and the color underneath the flack seemed consistent with the rest of the rock.

 

It is possible that it is a shellac. There is a shine to it and it doesn't seem to hide the underlying texture to the head shields. Do you know if there is a way to remove it? Denatured alcohol? 

 

@LabRatKing

Thank you for your feedback. What might explain this weird color cross-over though?

 

[LabRatKing]

1 hour ago, historianmichael said:

@FossilDAWG 

Unfortunately they are pretty well exposed already. I cannot seem to find a spot with more matrix around the head shields.

 

It is possible that it is a shellac. There is a shine to it and it doesn't seem to hide the underlying texture to the head shields. Do you know if there is a way to remove it? Denatured alcohol? 

 

@LabRatKing

Thank you for your feedback. What might explain this weird color cross-over though?

 

Looks like just the colors of the stone to me. I can see saw marks on it, I think. Not too clear when enlarged.

 

Dont remove the shellac. You will do more harm than good.

[traveltip1]

My fossil specimen, which I'm sure is real, is a cast of shields in what looks like a light brown colored siltstone. It's likely shellac on your specimen.

[historianmichael]

It seems like the general thought is that this piece is real, but covered in a shellac that has darkened over time. This would seem consistent with my initial thought that this piece came from an old collection that was purchased by the fossil dealer. Thank you all so much for the feedback! 

[JohnJ]

1 hour ago, historianmichael said:

What might explain this weird color cross-over though?

 

Sometimes the heat generated by a dull or dry diamond blade will alter the color of stone on the cut surface.

[historianmichael]

14 minutes ago, JohnJ said:

 

Sometimes the heat generated by a dull or dry diamond blade will alter the color of stone on the cut surface.

 

Thank you so much! That would make sense as the other side was also cut and has a similar grayish color to it.

[aeon.rocks]

What's the issue here? It's a cut stone. Layers on the outside, or near natural cracks, different layers, breaks etc. often show signs of weathering, mineral depositions, resulting in different coloration (pattina) than inside the matrix. 

 

The cut doesn't go through the specimen, right? 

[jpc]

As someone else mentioned, if it is shellac, do not remove it.  Removing shellac is a) very difficult  and b)  destructive.  

[historianmichael]

41 minutes ago, aeon.rocks said:

What's the issue here? It's a cut stone. Layers on the outside, or near natural cracks, different layers, breaks etc. often show signs of weathering, mineral depositions, resulting in different coloration (pattina) than inside the matrix. 

 

The cut doesn't go through the specimen, right? 

I was unfamiliar with old fossil preparation techniques, leading me to worry that this piece had been cast and colored to make it look like a genuine fossil.

 

Even though I understand now that it is likely a genuine piece, I still have concerns about the coloring caused by the shellac. Could it darken further over time? It sadly looks very unnatural. I am stuck in an internal debate over whether the rarity of the piece makes up for the appearance.