Pyritized Or Non-Pyritized Ammonites

[Melissawow]

I'll like to check out are these Arnioceras ammonites pyritized?

They are from Yorkshire UK. I want to know in your opinion, are these ammonites pyritized or non-pyritized?

Link to the picture: https://www.facebook.com/photo.php?fbid=10201976908256821&set=a.3256541024913.135604.1608741583&type=3&theater

[painshill]

I don't think there's any way to tell for sure... that's a monochrome photograph. The ammonite beds on the Yorkshire coast most usually yield specimens which are mud-infilled or pyrite-preserved, but also calcite preservation. Those look shinier than typical mud-infilled material (unless they've been polished up) but could be pyritized or calcited.

[Ptychodus04]

Based on the apparent color differences (even with a B&W photo), I would say calcite.

[painshill]

I really don't think you could be sure. Here's some of my UK examples converted to greyscale. Don't scroll down if you want to test your observation skills... I have put the original colour pictures below

GREYSCALES:

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COLOUR:

Edited September 16, 2014 by painshill

[Ptychodus04]

I still think hers are calcite. But, well made point!

[caldigger]

I don't think the photo that Melissa posted is black and white photography. It looks like those are the actual colors of the piece. Grey matrix and dark grey ammonites sitting on a really light grey table. The low (dim) lighting doesn't help matters either.

Edited September 19, 2014 by caldigger

[painshill]

I don't think the photo that Melissa posted is black and white photography. It looks like those are the actual colors of the piece. Grey matrix and dark grey ammonites sitting on a really light grey table. The low (dim) lighting doesn't help matters either.

Thanks Caldigger

I took a second look on a rather better/larger screen than previously and also downloaded the picture this time. You're quite right... it is a colour image, not greyscale. It's difficult to say how accurate the representation is in the photographs but I do now see a faint coppery tinge in places and my revised view would be that the preservation is essentially calcited mud with weak areas of pyritization.