Hi! I'm new here. Is this a coprolite?

[Roxana]

Hi! I'm new here and new to the fossil world. My husband and myself love going to the beach and looking for interesting finds. 2 years ago we found this odd glittery nugget on a beach Dorset, UK and I simply took it as I found it special. Placed it in our collection box and forgot about it. It seems that it cracked in the meantime as it fully dried out and it became easier to crack open. It is quite heavy for its size.. I have no idea what it is and it made me very curious, as I recently read about coprolites. Could this one be a coprolite? I will try and attach a photo where you could see the original shape. Thank you!! This community is amazing! 

[Darktooth]

Hello and welcome to the forum. I am not a coprolite expert but I think that this is geologic in nature. Looks like it has different mineral inclusions in it, possibly some pyrite. @GeschWhat is our coprolite expert. Let's see what she says.

[Roxana]

@Darktooth thank you for replying  initially, I also thought it might be pyrite, but I got a bit confused, as all the images I could find for pyrite are with fully formed crystals. Again, I know close to nothing about fossils and mineral formations, but I am eager to learn, and this forum is amazing 

 

[Mahnmut]

Hi,

as many other fossils, coprolites may contain pyrite or even be completely replaced by it.

Although sometimes original mineral content like bone tooth or shell material is preserved, very often the original structure of animal, plant or its leftovers is replaced by minerals that keep more or less detail of the shape, sometimes down to the cellular level, sometimes only a shadow. As coprolites do not start with as clear a structure as for example a skeleton, its sometimes hard to distinguish them. But GeshWhat will be able to tell you more.

Best Regards,

J

 

[pachy-pleuro-whatnot-odon]

Hi, and welcome to the forum!

 

I find it hard to estimate whether this could be a coprolite, as their shapes can sometimes be rather amorphous, especially when it concerns reptile coprolite. Lori would be able to help you based on the morphology, Below are a couple of examples from Lyme Regis for comparison.

 

 

 

My guess is that this piece "is just geological", as marine coprolites often show bone, fish scale and other inclusions - which, I believe, would survive, even if the rest of the coprolite (the "matrix", if you will) were to become pyritic (something, by the way, I haven't seen before). When I say "geological", however, it may very well be that your piece is the decay-product of another fossil. See, the thing about pyrite is that it's a mineral often enlisted by nature to permeate or completely replace organic matter with during fossilisation. That's probably why when you explicitly searched for it, you found the nice cubic crystalline specimens, rather than "golden" ammonites, "golden" shells, etc. (as an aside, pyrite is often confused with marcasite, a remarkably similar mineral that, as I understand it, is somewhat more stable in nature, however). Pyrite may even replace entire vertebrae or simply permeate them, given them a somewhat golden shine (hence the common name "fools' gold") when fresh. However, this will typically decay over time - into a solid black substance if you're lucky. For pyrite is a type (sulferic) iron rust, and the latter is it's stable decay product. Often, though, pyrite decay is way less stable, with it breaking apart into yellowish and white/greyish powders known as "pyrite bloom". This pyrite bloom can affect a fossil to such an extent that the entire piece may eventually entirely crumble into dust, if left untreated. This decay is also highly contagious to other pyrite-affected pieces in a collection, and is for that reason often referred to as "pyrite disease". Pyrite being an iron rust, however, also means that, given enough time, the mineral will eat away at a fossil, eventually making it look entirely amorphous. Such is the fate of many a pyritised ammonite from the Lyme Bay area I've seen...

 

I have no doubt, by the way, that your piece is pyrite-affected. Not only does pyrite glitter appealingly when fresh, leading to a lot of people - even those without an interest in fossils and/or minerals - simply picking it up, but your description of a "glittery nugget" fits the bill of microcrystalline pyrite perfectly. Not just that, though, as the fact that your piece fell apart is due not to dessication, but rather internal pyrite disease set in motion by the piece's initial contact with sea water (which one would normally rinse out by extensive amounts of soaking in subsequent "baths" of fresh water). Traces of this pyrite bloom can be seen in the white deposits on the inside of your piece and the orange/yellow outline around its core. As treating pyrite disease can be rather difficult and never gets you full 100% security against further/renewed decay, I'm afraid it might be best to simply get rid of the piece - unless it's a particularly sentimental piece and you're willing to invest the effort to stabilise it (there are ways, but none are particularly effective and some require chemical treatment). Sorry!

 

Anyway, lets first see what others make of your find

Edited June 12, 2021 by pachy-pleuro-whatnot-odon

[Coco]

I think it’s an unstable pyrite/chalcopyrite nodule. If it has an odor of sulfur (lit and extinguished match) it is that it is deteriorating and nothing will prevent it, unfortunately.

 

Coco

[Rockwood]

My first disappointing lesson on coprolites was nearly identical.

[Rockwood]

Some of them can produce neat needle shaped crystals if they decompose in the right conditions though.

That shelf in the bathroom that most people put towels on. That can do it. 

[GeschWhat]

Welcome to the forum!

 

When it comes to coprolites that have been replaced by pyrite, it is really hard to tell if they have anal origins unless you see inclusions. Yours does have mineral inclusions, but I don't see any thing biologic (bones, scales, etc.). Here is how it would work: The fresh poop would have been deposited in an iron-rich, environment with very little oxygen. Anaerobic bacteria would feed on the sulfates (the stinky stuff) in the poop and expel sulfides which would combine with iron to produce iron sulfide (aka pyrite - or what I like to call "poo-ls gold"). Sorry to disappoint but my best guess is that this is not a coprolite. It may have biological origins, but it is hard to say what might have been.  

 

[Roxana]

21 hours ago, pachy-pleuro-whatnot-odon said:

Hi, and welcome to the forum!

 

I find it hard to estimate whether this could be a coprolite, as their shapes can sometimes be rather amorphous, especially when it concerns reptile coprolite. Lori would be able to help you based on the morphology, Below are a couple of examples from Lyme Regis for comparison.

 

 

 

My guess is that this piece "is just geological", as marine coprolites often show bone, fish scale and other inclusions - which, I believe, would survive, even if the rest of the coprolite (the "matrix", if you will) were to become pyritic (something, by the way, I haven't seen before). When I say "geological", however, it may very well be that your piece is the decay-product of another fossil. See, the thing about pyrite is that it's a mineral often enlisted by nature to permeate or completely replace organic matter with during fossilisation. That's probably why when you explicitly searched for it, you found the nice cubic crystalline specimens, rather than "golden" ammonites, "golden" shells, etc. (as an aside, pyrite is often confused with marcasite, a remarkably similar mineral that, as I understand it, is somewhat more stable in nature, however). Pyrite may even replace entire vertebrae or simply permeate them, given them a somewhat golden shine (hence the common name "fools' gold") when fresh. However, this will typically decay over time - into a solid black substance if you're lucky. For pyrite is a type (sulferic) iron rust, and the latter is it's stable decay product. Often, though, pyrite decay is way less stable, with it breaking apart into yellowish and white/greyish powders known as "pyrite bloom". This pyrite bloom can affect a fossil to such an extent that the entire piece may eventually entirely crumble into dust, if left untreated. This decay is also highly contagious to other pyrite-affected pieces in a collection, and is for that reason often referred to as "pyrite disease". Pyrite being an iron rust, however, also means that, given enough time, the mineral will eat away at a fossil, eventually making it look entirely amorphous. Such is the fate of many a pyritised ammonite from the Lyme Bay area I've seen...

 

I have no doubt, by the way, that your piece is pyrite-affected. Not only does pyrite glitter appealingly when fresh, leading to a lot of people - even those without an interest in fossils and/or minerals - simply picking it up, but your description of a "glittery nugget" fits the bill of microcrystalline pyrite perfectly. Not just that, though, as the fact that your piece fell apart is due not to dessication, but rather internal pyrite disease set in motion by the piece's initial contact with sea water (which one would normally rinse out by extensive amounts of soaking in subsequent "baths" of fresh water). Traces of this pyrite bloom can be seen in the white deposits on the inside of your piece and the orange/yellow outline around its core. As treating pyrite disease can be rather difficult and never gets you full 100% security against further/renewed decay, I'm afraid it might be best to simply get rid of the piece - unless it's a particularly sentimental piece and you're willing to invest the effort to stabilise it (there are ways, but none are particularly effective and some require chemical treatment). Sorry!

 

Anyway, lets first see what others make of your find

Thank you so much! What a great explanation! And thank you for the references from Lyme Regis! We love exploring that area. I am not at all disappointed that it is not a coprolite. I am just excited to learn about what it might be. Your explanation about pyrite disease seems to fit to what happened to my "glittery nugget". It is indeed sad to hear it will keep decaying, but I will try and keep it in a box of its own, as I can't let myself throw it away

[Roxana]

2 hours ago, GeschWhat said:

Welcome to the forum!

 

When it comes to coprolites that have been replaced by pyrite, it is really hard to tell if they have anal origins unless you see inclusions. Yours does have mineral inclusions, but I don't see any thing biologic (bones, scales, etc.). Here is how it would work: The fresh poop would have been deposited in an iron-rich, environment with very little oxygen. Anaerobic bacteria would feed on the sulfates (the stinky stuff) in the poop and expel sulfides which would combine with iron to produce iron sulfide (aka pyrite - or what I like to call "poo-ls gold"). Sorry to disappoint but my best guess is that this is not a coprolite. It may have biological origins, but it is hard to say what might have been.  

 

Hi! Thank you for taking a look at my post! it is not at all a disappointment to hear it is not a coprolite. I was simply interested to see what it was and thought it might be a coprolite. I must say I followed your guide about coprolites, and even touched it with my tongue hehe, and no stickiness, no inclusions, but I only found your post after posting my question. Very interesting lessons! Thank you so much! 

Edited June 13, 2021 by Roxana

[GeschWhat]

3 hours ago, Roxana said:

Hi! Thank you for taking a look at my post! it is not at all a disappointment to hear it is not a coprolite. I was simply interested to see what it was and thought it might be a coprolite. I must say I followed your guide about coprolites, and even touched it with my tongue hehe, and no stickiness, no inclusions, but I only found your post after posting my question. Very interesting lessons! Thank you so much! 

You are very welcome. Yeah, the pyritized variety doesn't stick.  Actually, most of the UK variety doesn't - with the exception of some from the Oxford clay.