rust-like patches on shells

[lulu.shell]

Hello! I'm also new to the forum, so I don't know where to post this question. I have some shells with rust-like patches on them. Does anybody know how to safely remove this rust without damaging the shells? Can anybody tell me what it is caused by?

P.s. They are shells from an old collection.
Thanks in advance!

[dave r]

It could be anything, we really need photos so we can see what the problem is.
Dave

[lulu.shell]

Ok, thanks. I'll get back to you in a couple of days because I'm not currently at home. But I think I have heard of a bacteria that forms on old shells if they aren't properly stored, and these shells had been in contact with damp. I'll post photos in a few days!

Happy Easter!

[marlo]

There is a condition commonly referred to as Byne's Disease that can affect shells stored in certain conditions encoraged by damp.  However, it is not really a disease nor caused by bacteria.  See <a href="http://z14.invisionfree.com/Conchologist_Forum/index.php?showtopic=216" target="_blank"><!-- m --><a class="postlink" href="http://z14.invisionfree.com/Conchologist_Forum/index.php?showtopic=216">http://z14.invisionfree.com/Conchologis ... wtopic=216</a><!-- m --></a> for a discussion.

A rust-like discoloration is not entirely uncommon and can occur as a result of material the animal incorporates into the shell.  It would be helpful if you can ascertain whether the discoloration is part of the shell (in the enamel) or a deposit on it and if it may have occurred during storage.  If it occurred during storage through some mechanism, then it probably will at least partially rub off (assuming the shells were reasonably cleaned when placed in the collection).  This test will help determine the cause.  Photos would be a big help too.  <span class="petit">--Last edited by marlo on 2010-03-29 21:23:47 --</span>

[dave r]

Byne's disease leaves a chalky-white deposit and etches into the shell. Sadly I came across many cases when I curated a collection for my local museum. It also smells of vinegar due to the acid secreted by the fungus. I came across examples that looked like they had been dipped in flour. It attacks eggs too as they are also made of calcium.
It could be something as simple as periostracum still adhering or, as you say, contaminant from storage or just a discoloured shell due to environmental conditions. Hopefully the photos will show us which it is.
Dave  

[lulu.shell]

Pictures:

I have three shells with what appears to be rust. Can anyone suggest how to get rid of it? Will it pass on to other shells?

Thanks!

<a href="http://www.badongo.com/pic/9228204" target="_blank"><!-- m --><a class="postlink" href="http://www.badongo.com/pic/9228204">http://www.badongo.com/pic/9228204</a><!-- m --></a>
<a href="http://www.badongo.com/pic/9228206" target="_blank"><!-- m --><a class="postlink" href="http://www.badongo.com/pic/9228206">http://www.badongo.com/pic/9228206</a><!-- m --></a>
<a href="http://www.badongo.com/pic/9228211" target="_blank"><!-- m --><a class="postlink" href="http://www.badongo.com/pic/9228211">http://www.badongo.com/pic/9228211</a><!-- m --></a>

[dave r]

It certailly looks like rust. I think the shells may have been kept in a metal container or on something metal at some time which has rusted and stained the shells. This often happens in the tropics where the humidity is high or near the sea where the salt spray gets into things.It should not transfer itself to other shells unless they are wet and touching. As to how to get rid of it, I have no idea. I have seen this type of thing before and the rust seems to eat into the shell itself, all I can suggest is soaking in a strong bleach solution for a few days.
Sorry I can be of no further help.
Dave

[paul monfils]

I agree with Dave. These shells have been in contact with an iron source under wet conditions. Bleach won't touch these stains.  Actually they are not exactly "stains".  As Dave observed, such iron deposits seem to eat into the shell.  More precisely, they actually become part of the shell.  A brief chemistry lesson ... metals are arranged in what is called the electromotive series, or the replacement series.  Without going into the actual molecular changes that occur, suffice it to say that a metal higher in the series will replace a metal lower in the series in a compound containing that lower metal.  The shell of course is composed largely of calcium compounds.  Calcium is very low in the replacement series, and iron is quite high in the series, so when iron comes in close contact to a calcium compound in the presence of water (especially salt water), iron atoms actually kick calcium atoms out of the compound and take their place.  The only way to effectively remove the iron would be to expose the shell to a solution of a metal higher in the series than iron.  Two problems here ... first, most of the metals higher in the series than iron are very expensive and/or very toxic (cobalt, mercury, lead, silver, platinum, gold).  And secondly, any metal that would replace iron would also rapidly replace calcium.  So there you have it - such stains are essentially permanent.

There is one approach I have used occasionally to remove a light rust stain from a non-glossy shell like a Buccinum.  Application of a weak acid solution with a cotton swab, just on the stained area, will remove such a stain if it isn't too deep.  Vinegar will work but it's a very weak acid, so it will be slow going.  However, you should be aware that what you are actually doing in this case is removing the layer of shell in which the stain resides.  The stains on these nerites look pretty deep however.  You might have a chance with the conch, but frankly it probably isn't worth the effort on such a common inexpensive shell.  <span class="petit">--Last edited by Paul Monfils on 2010-04-11 20:06:37 --</span>

[lulu.shell]

Thank you so much for all your kind advice. I could not rightly say when the contamination with rust occurred. These shells were given to me by an old lady (a sought of aunt from my childhood)and I have had them in a plastic container away from all my other shells for years (probably a decade). Now, I am trying to organise my collection because I want to make an archive of what I have, I want to transfer them to little plastic bags. I will make sure I keep them separate from other shells.

[pam]

These look like the Red Sea species, Gibberulus gibberulus albus and Nerita sanguinolenta.  Are you sure that the staining is not from oil?  Oil spills are very common due to the heavy tanker traffic through the Suez Canal.  You might try some baby oil on a q-tip.