[NHCOLL-L:4158] RE: Cleaning oxidized pyrite mineral specimens

[CAHawks at aol.com]

I agree with Greg. Doesn't matter what treatment you apply, the only sure  
way to protect a specimen that has been decreptitating is to keep it below 30%  
RH. At that level, the oxidation becomes metastable.
 
Cathy
 
Catharine Hawks
Conservator
2419 Barbour Road
Falls Church  VA 22043-3026 USA
t/f 703.876.9272
mobile 703.200.4370  

 
In a message dated 1/14/2009 9:41:58 A.M. Eastern Standard Time,  
gbrown1 at unl.edu writes:

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
>  




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