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Wrangellian

chemical 'bloom' on fossil - ?

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Wrangellian

(Not sure of the tags I should use.)

This is the first instance I've found of any sort of 'bloom' on a fossil in my collection. Luckily it's not the best specimen but it is an echinoid and they are not as easy to find here as in some other places.

Sandstone from the Haslam(?) Fm on Vancouver Island.

Is this a calcitic bloom from some sort of acid or off-gassing from something in my storage media? I'm not sure how long this has been in this condition but I think it's happened within the last 10 years. I'm trying to keep things away from my collection that might cause this sort of thing. I've got wooden (not oak) cabinets, and the little white fold-up boxes with cotton or cloth substrate. I'm trying to get rid of plastics, foams or anything else questionable, and I can't think of what else there might be that could be a problem, unless simple humidity in the Summertime will do it. (This is indoors)

 

 

bloom 1.jpg

bloom 2.jpg

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ynot

I can not make out the surface of the rock very well, but it looks like natural crystal (calcite{?}) growth. Are You sure it was not there before it went into storage?

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Tidgy's Dad

Was it found near the Ocean? 

Maybe sea salt drying out and crystallizing. 

I soak my beach stuff for a few days where possible to remove any salt. 

 

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Wrangellian

Was not found near ocean. It's a very fine fuzzy-looking growth. Maybe mold? But I can't picture mold forming on a rock surface that has been in dry indoor storage for so long, and I'm 90% certain it didn't have this when it went in the box/drawer (maybe the unnoticeable start of it?).

The thickest part of it is on top of part of an ambulacrum/groove of the echinoid, if that helps you see what you're looking at.

 

 

bloom 1 det.jpg

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Bobby Rico
4 hours ago, Wrangellian said:

Maybe mold

That really looks like mold to me my friend. It must have looked dry when you put it away in your draws but maybe still retained some water. Better to be safe than sorry I would take the draws out of your cabinet and have a good look at the back . Cheers Bobby 

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ynot

:headscratch:

I am at a loss to explain this one.

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Wrangellian
14 hours ago, Bobby Rico said:

That really looks like mold to me my friend. It must have looked dry when you put it away in your draws but maybe still retained some water. Better to be safe than sorry I would take the draws out of your cabinet and have a good look at the back . Cheers Bobby 

Thanks but I'm not sure what I might expect to find in the back... there is no water source there or behind the unit.... and anyway this seems to be the only fossil with this growth (that I have noticed so far). I am concerned that the materials the cabinets are made of might be outgassing some sort of chemical that can react this way with calcite fossils/minerals.

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JohnBrewer

Some housing bricks do similar to this if they’re exposed to a lot of dampness such the side facing rain for example. They’re various salts, (mostly sodium and potassium salts) used in brick manufacture leeching out. If @Wrangellian it could be that it’s not salt free maybe?

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Wrangellian

I believe salts are the result of an acid/base reaction, no?

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siteseer

Hi Wragellian,

 

I have seen a fuzz or a build-up on fossils before.  It's almost always explained as a reaction to some solvent used to clean it.  Some people use vinegar (a mild acetic acid) to clean echinoids and I think that has led to a white build-up sometimes.  Did you use that to clean it?  You can try wiping it off with a little water or even acetone on a Q-tip to see if it comes off easily.

 

Jess

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JohnBrewer
19 hours ago, Wrangellian said:

I believe salts are the result of an acid/base reaction, no?

Or an acid/metal reaction which results in a salt and hydrogen. @Monica

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Wrangellian
17 hours ago, siteseer said:

Hi Wragellian,

 

I have seen a fuzz or a build-up on fossils before.  It's almost always explained as a reaction to some solvent used to clean it.  Some people use vinegar (a mild acetic acid) to clean echinoids and I think that has led to a white build-up sometimes.  Did you use that to clean it?  You can try wiping it off with a little water or even acetone on a Q-tip to see if it comes off easily.

 

Jess

I have never cleaned it with anything, except maybe a quick rinse in water but that would have been years ago. It has been sitting since then in the drawer, and I only discovered it when going thru my stuff looking for things to donate to the museum.

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Wrangellian

I've just recalled that this may have been outside in the woodshed a couple years ago for about a month while the indoor floor was being retiled. So it would have been exposed to damp air for a bit, but that alone doesn't seem sufficient to create a growth, unless it's mold. If it's chemical, I would think it would need a reactive agent in there in the first place, or am I wrong? So far it is the only specimen I've noticed with this growth. The only other thing that was affected by the stint outside was the big Hanksite salt crystal that I had (but it was nowhere near this echinoid).

Anyway, maybe I'll rinse it off and dry it nicely by the fire and hope it doesn't happen again.

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Al Dente

There might be some pyrite in your fossil. When pyrite breaks down it will form sulfate minerals. Here is a picture from the internet of pyrite beads with pyrite disease.

989C9109-037F-49AD-9EF7-AD667D751540.jpeg

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Wrangellian

That's a pretty drastic case!

I don't recall seeing anything like pyrite in the material from this location, but I guess it's possible if the xls are so small as to be invisible to the naked eye. It is plain sandstone with fossils of white 'shell' material, which has leached out in some spots leaving empty cavities (this ech has its shell mostly intact, but I believe it is all calcitic and no pyrite replacement).

I've read about certain materials such as oak cabinets releasing a type of gas over time that can react with any specimens made of calcite such as fossils and modern seashells, and I believe it leaves a thin white precipitate on the surfaces. It has been discussed elsewhere on TFF before. Thing is none of my cabinets are of oak. So what are the other possible culprits?

Do I need to do a taste test to see whether this fuzz is mold, salt or otherwise? :wacko:

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Plax

Am with Al on this one but not 100% sure of course. Little bits of pyrite/marcasite coating rusting? on the specimen. Not sure how to describe the chemical alteration of pyrite/ marcasite to iron oxide. Some of our more chemically  or minerologically inclined members can explain it. I could google it and quote wikipedia but where's the fun in that?

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