[NHCOLL-L:5513] pyrite disease

[Demouthe, Jean]

Dear Mr. Glotzhober:

Marcasite and pyrite next to each other will not cause pyrite disease (it's not called marcasite disease), although the products of the alteration may contaminate and affect other specimens around it.  Two of the alteration products of pyrite disease are hydrogen sulfide gas, which gives off a distinctive rotten-egg smell, and sulfuric acid, which will affect labels and specimens and storage trays under and near this specimen.

This "disease" is a series of chemical alterations that is triggered by moisture, and both of these mineral species are susceptible to it.

The reaction generally goes like this:

Iron sulfide + water goes to hydrogen sulfide gas + sulfuric acid + soluble iron sulfate.  The latter appears as a white powder on the specimen, and it is EXTREMELY poisonous.

The specimens may be cleaned by dry brushing in a well-ventilated area.  Protect yourself so that you don't breathe the dust.  If the deterioration has gone to the point where the specimen is falling apart, you might consider deaccessioning it and throwing it away.

If you are interested in natural history specimens and how to care for them, you might consider joining SPNHC, the Society for the Preservation of Natural History Collections.  Check out the web site at:  http://www.spnhc.org/

There are publications available that deal with the treatment and storage of "diseased" iron sulfide specimens, both in mineral and fossil collections.  Sally Shelton mentioned some of these in her e-mail.  I would like to add The Care and Conservation of Geological Material, 1992, Frank Howie, editor.

Good luck

Jean DeMouthe


Dr. Jean F. DeMouthe
Senior Collections Manager for Geology
California Academy of Sciences
55 Music Concourse Drive, Golden Gate Park
San Francisco, California 94118
jdemouthe at calacademy.org<mailto:jdemouthe at calacademy.org>
(415) 379-5258



From: owner-nhcoll-l at lists.yale.edu [mailto:owner-nhcoll-l at lists.yale.edu] On Behalf Of Bob Glotzhober
Sent: Wednesday, June 15, 2011 5:55 AM
To: NH Collection List Server
Cc: Brad Lepper; Jason Crabill
Subject: [NHCOLL-L:5511] marcasite disease

I need some help understanding better what has been called "Marcasite Disease."  As curator of all our relatively small natural history collections (circa 29,000 cataloged items) within our state historical society museum, I deal with all types of natural history collections - and minerals are one area that is not within my expertise nor training. (But I keep on trying to learn!)

I recently had a visit by a couple of mineral collectors - who seem very knowledgeable. They noticed in our exhibits that we have a nice specimen of marcasite adjacent to a nice pyrite. It seemed logical as they are related types. They said that having these in close proximity would cause marcasite disease - eventually destroying the pyrite. This concerned me, as specimens of both not on exhibit are also stored in the same collections cabinet. Therefore, many specimens are within the same cabinet, although on different shelves. I talked with a more mineralogically knowledgeable friend, and he said he thought (though not certain) that "marcasite disease" (not really a disease) affected mostly marcasite and was now thought to be primarily a humidity problem.

Which of the above is correct - or are both somewhat correct? Do I need to move my exhibit specimens to separate them, and if so - how far apart? Do I need to re-shelf our collections so these are in different cabinets? Or am I AOK?

Bob Glotzhober

===============================

Robert C. Glotzhober                           e-Mail:  bglotzhober at ohiohistory.org<mailto:bglotzhober at ohiohistory.org>

Senior Curator, Natural History                        Phone  614-298-2054

Ohio Historical Society                         Fax      614-298-2089

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