[NHCOLL-L:4157] RE: Cleaning oxidized pyrite mineral specimens

[Gregory Brown]

Robyn,

I hesitate to contribute to this thread since you have already heard from some of the best minds in
geological conservation and I'm merely a vertebrate paleo preparator, but...

Two things you might want to keep in mind, one perhaps more philosophical, one practical: 
1) To borrow loosly from Freud...sometimes a cigar is just a cigar, or in the case of minerals, sometimes
(depending upon mineral species) oxidation, although perhaps not aesthetically pleasing, is a legitimate
part of the mineral specimen. Removal in that case is neither necessary nor wise since oxidation (again,
depending upon mineral species) is not necessarily damaging and treatment itself may be! (Obviously, if
you are actually dealing with pyrite decay, this does not apply.)

2) If cleaning is warranted, it is only the first step.  All treated specimens, at the very least, must
be provided with a storage environment that effectively controls RH levels to prevent a recurrence of the
problem.  Contrary to some proprietary claims, there is no effective treatment (sealant, consolidant or
other goop) that can prevent pyrite oxidation in a specimen stored in high RH.  Depending upon the
specimen, you may even want to consider anoxic enclosures.

I'd recommend consulting with a mineral conservator that can look at your actual specimens and determine
the best treatments.  Also recommended: The Care and Conservation of Geological Material: Minerals,
Rocks, Meteorites and Lunar Finds by Frank Howie(Butterworth - Heinemann Series in Conservation and
Museology) and the excellent three volume Science for Conservators series published by the Museums and
Galleries Commission.  These references are very helpful in providing a non-conservator with the basic
information they need to assess the value and appropriateness of treatments they may be considering.

Greg

Gregory Brown
Chief Preparator
Vertebrate Paleontology
University of Nebraska State Museum
W-436 Nebraska Hall UNL
Lincoln, NE 68588-0514
402.472.2657
GBROWN1 at UNL.EDU 




> -----Original Message-----
> From: Robyn Hodgkins [mailto:hodgkins at chem.ucla.edu] 
> Sent: Friday, January 09, 2009 12:54 AM
> To: NHCOLL-L at lists.yale.edu
> Subject: [NHCOLL-L:4140] Cleaning oxidized pyrite mineral specimens
> 
> 
> I am a UCLA chemistry graduate student helping the Natural History 
> Museum of Los Angeles County Mineral Science department. They have 
> several minerals containing iron sulfides that have become brown in 
> color. The corrosion has not been completely identified, but 
> we believe 
> it is mainly oxidized pyrite corrosion. The Museum is interested in 
> cleaning these minerals. I have found literature about using 
> ethanolamine thioglycollate to clean. Has anyone used this or has an 
> opinion of how this would compare to Super Iron Out? thanks!
> 
> Robyn Hodgkins
> Graduate Student
> Garrell Group
> UCLA Chemistry and Biochemistry
> hodgkins at chem.ucla.edu
> 310-206-9434
>