Pyrite Oxidation: Where Are We Now?

Written by Deborah Hutchinson, Geology Curator at Bristol Museum & Art Gallery.

Natural History Museum, London – 10th May 2018

We have all been there; you open a box/drawer/cupboard that possibly has not been opened in a very long time. Then that sulphurous, acid smell hits you, and you see the yellow and white fluff all over your beautiful specimens! – ‘Pyrite! Argh, quick, call the Conservation Team’. This one day workshop organised by the Geological Curators’ Group and the Natural History Museum, London addressed the causes, trauma and treatment of this pesky problem inherent in all geological collections through posters, talks and very importantly- practical hands-on experience (if you were one of the lucky ones that was able to hang about in the afternoon).

The jam packed day started with coffee (always very welcome after travelling) while the fifty or so delegates gathered and mingled at the Flett Lecture Theatre (NHM) before the morning session of talks began. The talks were an insight on a range of pyrite related topics. I was sat with one of my conservation colleagues who sighed and nodded all the way through most of the slides, including a rundown of the signs of pesky pyrite:

  • Sulphur smell
  • Loss of surface shine
  • White/yellow powder
  • Expansion cracks
  • Acid burns on packaging

Sadly, I have seen them all!  Other talks looked at past examples of pyrite care from the NHM; Project Airless which is also at the NHM; the problems in displaying material that can exacerbate pyrite oxidation; how we as curators care for collections afflicted with pyrite; and things to think about for the future. If you are a member of the GCG, you will have access to videos of the talks on the GCG website, so you can go and see for yourself.

Kieran Miles (NHM) describing the chemistry of pyrite oxidation. © Deborah Hutchinson.

The morning session was broken up with posters mostly focused on the various projects that institutions have carried out. This was a lovely opportunity to see what has been done already and of course to mingle and chat with colleagues.

Lunchtime allowed me to get my first glimpse of ‘Hope’ the blue whale in Hintze Hall, and to spend time exploring the galleries at the NHM. I always go back and look in on some of my favourite marine reptile specimens when I’m visiting (and obviously I need to visit the bookshop!).

‘Hope’ the blue whale, welcoming visitors at the NHM. © Deborah Hutchinson.

The afternoon was the practical side of the day which I’d been looking forward to the most. The group was split in two with each group swapping schedules halfway. My group started with a hands-on guided exploration of the different forms that pyrite can take in geological collections, with an opportunity to have a go at basic dry cleaning. One of the best (and cheapest) tools for this are basic make-up sponges (thanks for the top tip).

A poorly ammonite, ready to be ‘dry cleaned’ to remove efflorescence with a makeup sponge (white sponge at the top) no less and a traditional conservation sponge (cream sponge at the bottom). © Deborah Hutchinson.


Lucia Petrera (NHM) demonstrating the many forms pyrite can take. © Deborah Hutchinson.

We were then whisked off for a behind the scenes tour of the stores, which is every curator’s favourite bit of any trip to a museum that they don’t work in! We walked up hundreds of stairs and past miles of poster-lined cabinets to reach drawers of ammonites that had undergone repackaging as part of the NHM’s Project Airless. It was really useful to see in practice the footprint increase a storage box has, once it has been repackaged in an anoxic micro-environment. Apparently now researchers are reluctant to open sealed bags to actually access the specimen!

Zoë Hughes (NHM) leading a store tour at the NHM, showing some specimens treated as part of Project Airless. © Deborah Hutchinson.

We were then treated to a trip to the Conservation Department (back down all those stairs…) for another sneak peek, this time at where and how conservators care for collections. Cue lots of questions (and expert answers) for Lu Allington and her team.

Jenny Gosling (Bristol Museum & Art Gallery) observing the collections in the Conservation Department. © Deborah Hutchinson.

After a quick break, it was then time to muck in with plastazote, scalpels and oxygen scavengers, and have a go at hands-on repackaging. We were provided with all the kit we would need and again had expert guidance to carefully cut plastazote packaging for our fossils, package original labels in Secol envelopes and to create ‘gift-style’ bags of barrier film into which we placed our pyritic patients. The tricky bit was not losing your fingers in the heat-sealer… it had quite a bite.

Some of the kit you will need to repackage your specimens in an oxygen free environment. © Deborah Hutchinson.


The heat-sealer at the NHM is vicious, mind your fingers! © Deborah Hutchinson.

In all, this was a much needed and welcome day of theory and practical with an opportunity to ask questions. I left feeling that I could return to the collection I care for and implement positive changes. More of the same please GCG!

I am officially competent. Now, is that a lion or a hedgehog in the image? © Deborah Hutchinson.


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