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Meteorite Preservation


I have purchased a book entitled 

   The Care and Conservation of Geological Material:
   Minerals, Rocks, Meteorites and Lunar Finds
      edited by Frank M. Howie

It was a rather expensive book ($89) for only a small amount
of advice (in my opinion), but the field is narrow and the experience
is specialized.

I thought I'd summarize what I learned upon first reading.

The target audience is the curator of a museum.

Most of the info is related to mineral storage.

I'll cover some of the important stuff related to meteorites.

I'll skip the parts related to Lunar material storage at Houston -
they have a special hermitically sealed room supplied with extra-dry
liquid nitrogen, and only allow Teflon, aluminum, and stainless steel
to touch the material. Clearly this is outside the realm of the possible
for most readers of this list.

I will cover the stuff that we can all use.

What harms meteorites, what can we do to minimize change?

1) Oxygen + Water = rust

  This is the most common cause of problems. The solution (no pun
intended) is to save them in a low relative humidity < 30%.
  Sealing a sample in a polystyrene bag, then putting that bag in
another bag with a dessicant such as Drierite is a feasible method.
  Drying in anhydrous ethanol is also quite helpful, but be sure to
dry it for some time, a short period may only leach out some minerals.
  
  I soak my meteorite specimens (except for friables and carbonaceous
types) like this:
    1) rinse out a glass container with ethanol
    2) soak the meteorite for a short time, then drain
    3) soak again overnight or longer
    4) dry in an oven for a few hours at about 200 F ("Warm")
    5) move to dessicating chamber and store permanently

This is what I have done and the advice in the book endorses this
approach.

2) Don't touch - if necessary only touch fusion crust. Oils, salts
   and human waste products are not good for specimens.

   I use latex gloves when I handle specimens that have gone through
   the drying process above. You can get a hundred gloves for about
   $20 US.

3) Chlorine and lawrencite.

   Chlorine is not found in meteorites. When chlorine is present, the
   metal reacts to form lawrencite. Therefore, don't rinse with tap
   water (which is usually chlorinated) - use distilled water.
   Drying in ethanol helps if this happens.

4) Storage and containment.
   The double bagging was already mentioned. However, most will want
   to display to some extent, so the meteorite will be touching
   something. Here is a list of materials and their long-term affects:

   Wood - volatile organic acids can attack metals and sulfides
   Paper, cardboard, etc.  - acid, formaldehyde, sulfur dioxide
         - use acid-free paper only
   Acrylic, polystyrene - no problem
   ABS - no problem
   Epoxy - no problem after curing
   PVC - emits hydrogen chloride - avoid
   Epoxy paints - no problem after drying
   Acrylic paints - can emit acetic acid and methacrylic acid which
        can corrode metals and sulfides
   Latex paints - emits ammonia and hydrogen sulfide - avoid.
   Shellac - no problem
   Oil-based paints and varnishes - emit aldehydes and organic acids -
                                    avoid
   Textiles - emit organic acids and hydrogen sulfide - avoid
   
Cutting:
  
   The book recommends cutting with a wire saw - a wire on a bandsaw
   that is coated with corundum. Mininises heat and lossage.

   Another method is just to hit it with a stainless steel hammer!
   No loss, not much damage. Honest, this was mentioned!
     
The book covered harm caused by moisture light, damage to special
materials, harm to the curator due to hazardous materials, and many 
other topics.

I tried to outline a simple approach that seemed to follow
recommendations in the book.

Meteorites are precious and irreplaceable. We, as collectors, should
do our part to make sure that this material is available to future
generations.

A simple method of drying with anhydrous ethanol, storing touching an
acrylic plastic, in a dry environment, and using shellac as a coating
agent (if deired) are recommended.

For myself I do all this except I have use acrylic gloss spray paint
on pallasites and some meteorites. I have found that acrylic spray
paints can be removed in moments by soaking in acetone. I'll look
these things over after a few years and see what happens.

-- 
          Jim Hurley
       Arachnaut's Lair
http://www.arachnaut.org/ >
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