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aplomado

How altered are these ammonites?

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aplomado

I would like to buy more ammonites.


I like ammonites without excessive alteration usually.


Most of the white ammonites I see for sale are described as "polished" like the ones in the picture below.

 

Are these just cleaned up, or is the shell actually damaged or altered in some way?

 


s-l1600.jpg

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Tidgy's Dad

Look like pretty good Madagascan Perisphinctes to me. :)

 

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RuMert

There's no shell probably - steinkern

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Ruger9a

They're fine and nice looking quality.

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caldigger

For that polish it is just a good cleaning and probably buffed a bit. Not the deep "polish" that takes all the outer layer off like so many we see.

These retain the shell material. A steinkern would not have the decorative pattern we see on these.

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FossilDAWG

They look good to me.  I think the shell is present, as I don't see the suture lines and they should be visible on a steinkern.

 

Don

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Ludwigia

They do look like they've been ground down a bit for a light polishing, but they look quite alright to me as well.

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FranzBernhard

I agree with @Ludwigia:

1 hour ago, Ludwigia said:

They do look like they've been ground down a bit for a light polishing

Its a matter of taste, if you like this kind of treatment. I don´t like it. I like to have them cut right through the middle... :DOH:.

However, it is unusual for Madagascan ammos not to have the aperture cut off (Very good!!). Where do they come from?

Franz Bernhard

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aplomado
28 minutes ago, FranzBernhard said:

I agree with @Ludwigia:

Its a matter of taste, if you like this kind of treatment. I don´t like it. I like to have them cut right through the middle... :DOH:.

However, it is unusual for Madagascan ammos not to have the aperture cut off (Very good!!). Where do they come from?

Franz Bernhard

 

I found the picture on our favorite auction site... they are shipped from China... I can't find the original listing.

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Tidgy's Dad
Just now, aplomado said:

 

I found the picture on our favorite auction site... they are shipped from China... I can't find the original listing.

Some Chinese sellers seem to get bulk lots of fossils from Madagascar and then sell them on.  

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caldigger
5 minutes ago, Tidgy's Dad said:

Some Chinese sellers seem to get bulk lots of fossils from Madagascar and then sell them on.  

Yep, in fact you will likely find more Madagascar items for sell coming out of China than you will coming straight from Madagascar. 

These two look good, I wouldnt hesitate to purchase them. Actually I have several in my personal collection myself.

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Tidgy's Dad
8 minutes ago, caldigger said:

Yep, in fact you will likely find more Madagascar items for sell coming out of China than you will coming straight from Madagascar. 

These two look good, I wouldnt hesitate to purchase them. Actually I have several in my personal collection myself.

I have one which I rather like, but it has had the aperture chopped off as @FranzBernhardmentioned. 

Perisphinctes1.thumb.jpg.9cd55fec6f1c3ae6f538919f29fb9d7d.jpg

Which is why the ones on offer here look pretty good. 

 

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FranzBernhard
25 minutes ago, Tidgy's Dad said:

have one which I rather like, but it has had the aperture chopped off

Arrgh!! But it is much less polished (maybe totally unpolished) than those in the starting post.

Well, obviously you can not have both (unpolished and uncut aperture), because fossils from Madagascar must be altered in some way if they have to be exported.

Franz Bernhard

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Johannes
On 20.12.2019 at 8:35 PM, FranzBernhard said:

Arrgh!! But it is much less polished (maybe totally unpolished) than those in the starting post.

 

 

Ammonites from those madagasan Upper Jurassic sites vary in a broad range of preservation states of there shell. The last shown specimen is quite weathered, but there are even some reduced to steinkern preservation. On the other site, you can find sometimes unpolished ammonites in mother-of-pearl-preservation from those deposits.

 

If you want to deem the first ammos shown above are polished you have to take a carefull view on differences between the outer and the inner whorls. If you are lucky, "polished" only means a shlight brushing to remove the rock matrix...

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