Hello Nigel,
I have found that "mineral" pyrite keeps better than "fossil" pyrite if
you know what I mean. And even then igneous and metamorphic mineral
pyrite seems to tarnish less quickly than sedimentary.
The reason I guess for fossil pyrite decaying rapidly is that it is made
up of lots of tiny spheres and therefore has a huge surface area
compared with a large cubic xtal. Material I collected from Lyme Regis
and Charmouth suffered badly. Also pyrite in fossil wood and jet is a
b*gg*r!
Cheers, Mike
-----Original Message-----
From: The Geological Curator's Group mailing list
[mailto:[log in to unmask]] On Behalf Of Nigel R. Larkin
Sent: 16 October 2012 10:46
To: [log in to unmask]
Subject: Predicting pyrite decay - your help requested, please.
As there isn't a definitive guide one can turn to that lists sites
yielding specimens likely to suffer from pyrite decay if storage
conditions are less than ideal I would like your help to put together
some guidelines that could be published in the Geological Curator /
NatSCA or somewhere similar.
If you have had fossil or mineral specimens suffer from pyrite decay
please get in touch (see below) and give me the details. Also, tell me
about any sites and/or geological horizons that you know yield specimens
that suffer particularly badly or easily from pyrite oxidation, even if
you know of only a few examples. This includes minerals as well as
fossils. A locality name is essential (as detailed as possible, but if
all you have is 'Whitby area' that will do) and include as much
stratigraphic information as you have. It would be useful if you could
indicate the sort of material, i.e. 'ammonites' or 'marine reptiles' etc
and (it is usually unlikely one would know the following) whether the
pyrite decay is active only in the matrix surrounding the specimen, or
only within the specimen, or in both.
Also, please send me references for any published papers you know of
relating to pyrite decay. Please ask ex-curators and other relevant
colleagues for their input. The more people that contribute, the more
reliable and useful the end result will be.
I will put all the information together and will publish a list of sites
known to produce particularly susceptible material. This would be a
useful starting point for curators either wanting to round up material
to put in a better (low
RH) microclimate or those wanting to check targeted parts of their
collection once a year.
Please reply off-list so we don't clog-up everyones' mailboxes. Many
thanks for your help.
Nigel Larkin.
Email: [log in to unmask]
Nigel R. Larkin BA MSc
http://norfolk.academia.edu/NigelLarkin
http://www.natural-history-conservation.com
http://www.facebook.com/#!/pages/Natural-History-Conservation/1193467980
95177
Research Associate (Geology),
Norfolk Museums and Archaeology Service, Shirehall, Market Avenue,
Norwich, Norfolk. NR1 3JQ.
http://www.museums.norfolk.gov.uk
Associate Member of the "Ancient Hominid Occupation of Britain Project"
http://www.nhm.ac.uk/hosted_sites/ahob/
Telephone: 07973 869613
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