Coal

Sebastian Foxley <bowtieseb [at] hotmail__com> writes

>We have a piece of coal in our collection, which was mounted on a
>pack to commemorate the opening of a mine.  The coal is now
>suffering from what we think is pyrite disease; yellow spots have
>appeared on the surface, the coal is splitting and braking apart and
>some of the coal has deteriorated into a grey powder.  Acid free
>paper next to the worst affected parts of the object has also become
>yellow and brittle.
>
>Is there anything I can do to stabilize this object or prevent to
>similar items going the same way.

Your description matches my observations of coal samples affected by
oxidation of pyrite within reactive-pyrite-rich layers.  A
geological conservator or the Palaeontology Conservation Unit at the
Natural History Museum could confirm your diagnosis and could advise
on an appropriate treatment.  Chemical treatment will not likely be
of significant benefit. Anoxic storage is probably the best
approach.  Again, after inspection of the object, an expert can say
whether dry or moderate RH anoxic storage would be best.

Robert Waller, Ph.D.
Chief, Conservation
Canadian Museum of Nature
PO Box 3443, Stn D
Ottawa ON K1P 1P4
613-566-4797
Fax: 613-364-4027


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                  Conservation DistList Instance 18:1
                  Distributed: Thursday, June 17, 2004
                        Message Id: cdl-18-1-002
                                  ***