[NHCOLL-L:1584] Pyrite decay Information

[Adrian M Doyle]

Dear NhColl subscribers,

As one of the authors of the paper 'Use of Ethanolamine Thioglycollate in 
The Conservation of Pyritised Fossils' (Palaeontology vol 27 part 2 1984 pp 
421-424) I am happy to send copies of the paper to any interested party.

The technique has been very successful on a variety of actively decomposing 
pyritic specimens (both dry and silicone fluid preserved) and alongside an 
alternative treatment devised by Rob Waller 'Waller,R. 1987: An 
experimental ammonia gas treatment method for oxidized pyrite mineral 
specimens'. Preprints (Working Group 13), 623-630. ICOM Committee for 
Conservation. 8th Triennial Meeting Sydney, Australia, 6-11 September, 
1987. Getty Conservation Institute, Los Angeles,  is effective for already 
damaged material.

However, my main experience suggests that prevention is better than cure; 
by maintaining a low humidity (usually recommended at lower than 40%) the 
probability of pyrite breakdown occurring is significantly decreased.

The use of microclimates (using 'stewart' boxes or barrier film enclosures, 
ie 'marvelseal' or 'escal') is an effective way of preventing damage in a 
diverse collection without full-scale humidity control.

I also recommend that even after treatment, all treated material is kept in 
a low humidity to prevent further 'outbreaks'.

This may be due to the inability of the treatments to neutralise and/or 
remove any of the remaining actively decaying microcrystalline pyrite and 
we have examples in our collections where the oxidation has re-activated as 
a result of unsuitable humidity levels.

It is sometimes difficult to recognise 'pyrite decay' but a simple test 
with pH paper showing an acid is usually sufficient; indeed the sulphurous 
smell, white/yellow 'cigarette ash' appearance is usually a give away - 
once discovered it is not forgotten!

A research project (unpublished) conducted in 1996 at The Natural History 
Museum Palaeontology Department (London, England) of over 500 invertebrate 
specimens specimens treated for pyrite oxidation, provided us with data 
suggesting that the Ethanolamine Thioglycollate treatment was effective 
although lack of detailed records makes long term assessment extremely 
difficult.

A detailed photograph and or cast of important specimens which are actively 
decaying is therefore sometimes prudent.



Mr Adrian M Doyle
Conservation Scientist
Palaeontology Conservation Unit
Department of Palaeontology
The Natural History Museum
Cromwell Road
London SW7 5BD
U.K.

Find out more about the Palaeontology Conservation Unit at :

http://www.nhm.ac.uk/palaeontology/cons/cons.html
http://www.nhm.ac.uk/science/consulting/fossildetail.html

email: amd at nhm.ac.uk
voicemail: +44 (0)20 7942 5116
fax: +44 (0)20 7942 5546


IMPORTANT NEWS:  There will be a phased, temporary closure of the NHM
Palaeontology Building from 2002 to 2004 while a major refurbishment
project is carried out.  Though no timetable has been formally approved
yet, from 1 January 2002 substantial parts of the collection and other
facilities will become unavailable for periods of approximately 6 months at
a time.  For more information see the Palaeontology Department's website,
http://www.nhm.ac.uk/palaeontology, Environmental Refurbishment Project.
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