The problematic specimen is a fossil endocast of a calamite stem from the Carboniferous. It contains some pyrite and the oxidation process is already running. What is the best method to stop the decomposition and to preserve the fossil?
The only way to stop and revese the decay is treating it with Glyzerine under vaccum, thta's how we treated hundreds of pyrite ammonites and plants from the Triassic in the Natural History Museum Basel.
Ther is also a paper about it in the Journal Der Präparator. You can contact Antoine Heitz at the Msuem he might be able to send you a PDF
Keep it as dry as possible... in various internet forums you find recommendations like removing the oxidized bits, keeping the fossil in sealed plastic containers, and putting a desiccant bag (silica gel) into it. My impression is, though, in the long run nothing stops entropy...
you already answered the question you asked, keep it dry and in reducing media, you can add the epoxy or any good resin to prevent the Oxygen from the pyrite.
The problem is, if you add anything to cover it in some cases, as with plants you will destroy the primary organica matter and/ore make it impossible to do any analytical analyses later. Thus keep it dry is the only way of hope in order to keep it as long as possible.
Thank you very much for all answers.
I see this problem is not completely resolved.
I think covering the fossil may still leave some undesired oxygens.
Take a small metal or glass container, and float it in a pot of water that you heat on a stove. In cooking, this method is called au bain-marie, and it is used where a steady, gentle heat is needed. Using this method, heat the wax to somewhere above 40°C, until it turns to a clear, almost watery liquid.
Dip the fossils in and then maneuver them around to get the wax everywhere. Use forceps or a skewer or something like that if the wax gets too hot to touch (it needn't do, though). When the fossil no longer produces bubbles, remove it and allow it to cool; the wax will solidify and seal the fossil, safeguarding it from oxygen.
Afterward, use a fine cloth to polish off some of the excess wax; a very thin film is plenty to keep the atmosphere out, and the wax tends to dry with some ugly drips.
Dear Arkajyoti Pathak,
thank you for the description of this interesting method.
Hello, Michael,
We use diffusion-proof, transparent plastic bags in our collection to seal specimens containing pyrite. The specimen comes together with a moisture adsorber into this tube and the ends are thermally welded. Optionally, the bag can be filled with nitrogen before sealing to displace humid air.
We have been using this method for several years - certainly more than 10 years. The results are very good.
In some cases, pieces sealed in polywax in the 80s were sealed in this way. In many cases the method with the wax was not able to stop the decay of the pyrite, but apparently trapped moisture in the pieces!
I can send you photos of our method if you want
Good luck with the conservation.
Many greetings,
Achim
Hello Achim,
thank you very much for this helpful information.
Some photos would be nice.
Best wishes,
Michael
Hi
some advices to soak the fossil in a reducing agent like hydroquinone, let the fossil dry, and again 2 or 3 cycles. Archaelogists use different reactives to preserve pyrite rich artefacts.
The only way to stop and revese the decay is treating it with Glyzerine under vaccum, thta's how we treated hundreds of pyrite ammonites and plants from the Triassic in the Natural History Museum Basel.
Ther is also a paper about it in the Journal Der Präparator. You can contact Antoine Heitz at the Msuem he might be able to send you a PDF
Thank you very much. Do you mean the article: Krogmann and Lehmann (2009): Anwendung von Mikroklimaten in der Konservierung von Pyrit und Markasit"?
here:
Weick, M. (2011). Pyritbehandlung von fossilem Wirbeltier- und Wirbellosenmaterial durch Ammoniakbedampfung und Paraffinierung mittels Vakuum. Der Präparator 57:6-31.
That's indeed how we do it at the Museum in Basel, and it works pretty well, with about 10-15 years of experiment, the specimens haven't changed and are still very stable.
Best wishes
Taking advantage of this thread, I would like to ask you a more philosophical question. Do you think that if the oxidation process is already running, it is still a taphonomic process? or did the taphonomy end when the fossil was collected?
I think the discrimination between natural and induced taphonomy comes into account to describe the degrees and processes
It depends on how you define taphonomy and when it finished. In the classical sense of Efremov (1940) taphonomy includes all biostratinomical processes after death of an organism, the burial in the sediment and the process of fossilisation.
The question is when fossilisation is finished, because fossils in the lithosphere are permanently exposed chemical and physical influences and underwent more or less modifications.
I think taphonomy at least ends when a fossil is excavated, because then it will not be any longer part of the lithosphere. The processes after excavation I would consider as weathering, because the rock is in direct contact with the atmosphere.
The calamite fossil in question was mined and deposited at a mine dump in the 1960´s. I collected it in the 1990´s on the mine dump. In all probability pyrite decomposition began during the last 50 years when it was exposed to atmospheric oxygen. Therefore, I think pyrite decomposition of the calamite endocast is rather a process of weathering than a taphonomical process.
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