[NHCOLL-L:1579] Re: fragmenting fossils

[Steve Jabo]

The only way I've heard of treating iron sulfides is to passively expose them to an ammonium hydroxide vapor in a sealed container for a few hours - ideally with polyethylene glycol (PEG 400). This will precipitate the iron out as an iron oxide and stop any further crystal growth. This will not reverse any damage, and will turn the specimen brick red in the areas of crystal growth, but is harmless. Any oxide can be carefully removed manually or with low-pressure air abrasion. The specimen must then be sealed in an airtight container in the collections.
Chris Collins at AMNH introduced me to this procedure and it works well.

Regards,

Steve Jabo
Vert. Paleo Prep Lab
Dept. of Paleobiology
Smithsonian Institution
P.O.Box 37012
Natural History, EG-4, MRC-121
Washington, DC 20013-7012

202.357.2221


>>> Martin Tillett <mtillett at UMD5.UMD.EDU> 04/23/02 09:03PM >>>
Your fossils probably have iron sulfides in them and the white residue or
powder is from sulfuric acid. Very much like the stuff that grows on car
battery terminals. Once the process starts it is the beginning of the
end. I have delayed the disintegration process by placing the fossils in a
sealed jar with distilled water. Over time the fossils still
disintegrate. I found several beautiful fossilized cones from fir trees
that were replced with marcasite only to watch them crumble into dust. It
seems that once the specimens are removed from sediments and exposed to
air that oxidation takes over and reacts to the iron sulfides. If anyone
knows of a treatment please share. I have communicated with specialists in
the past and no one knew of any way to "cure the sick fossils".
Martin Tillett

On Tue, 23 Apr 2002, Larkin G. Chases wrote:

> Hello, 
> 
> I was wondering if anyone could give me some advise regarding the
> crystallization and fragmentation of fossils. A few of our fossils are
> growing white crystals which results in the specimen crumbling. There is
> also an acidic smell to the specimens. Is there a way to stop this reaction?
> 
> Also, I noticed that rusty-brown dust is appearing on some of the specimens.
> Possibly iron? Is there a way to stop this?
> 
> Thank you, Larkin
> 
> ****************
> Larkin G. Chases
> Museum Assistant
> HSU Natural History Museum
> 1315 G Street, Arcata CA 95521
> Phone: (707)826-4479
>