[meteorite-list] Curation of meteorites containing organics

From: Jim Wooddell <nf114ec_at_meteoritecentral.com>
Date: Mon, 30 Apr 2012 08:20:38 -0700
Message-ID: <C9301A078BF043D7835F93D6FB2C71C5_at_Grande>

Hi Carl and all!

This is an important topic as I think most experience hunters will comply
with sound advice. I brought this up because what I am seeing in the field
first hand does not appear to be working well at all! Now, it might if the
specimen is immediately placed in an additional protective container and not
moved or messed with again, but with 90% or more of the finds, that is just
not happening.

Issues to consider are not only contamination, but the effects any metal has
on other metals and metal oxides and sulfides.

Just off the top of my head, Galvanic corrosion which occurs immediately
upon contact. Then there is the Peltier Effect (thermocouple reaction) and
the Thomson effect.

Excluding any of the corrosion issues, it is also very much related to
handling issues.

It is very evident the fragments of this Sutters Mill meteorites can easily
crumble. The specimens with complete 100% fusion crust are better
protected, but when I was there, only a few had been found at the time.
Most were fragments.
That known, putting them in aluminum foil DOES NOT help that issue.
Instead, I think it makes it worse.

I've always followed this which is in our CFR's:

(1) Handling requirements. Handling procedures shall ensure that the
specimens are properly labeled and handled to minimize the potential for
contamination from the point of collection to the point of curation. At a
minimum, handling procedures shall include:

(I) Handling the samples with clean Teflon or polyethylene coated implements
or stainless steel implements (or equivalent);

(ii) Double bagging of samples in Teflon or polyethylene (or equivalent)
bags;


While Teflon bags (PTFE) are likely inert, polyethylene bags should be a
good short term field storage.

So, as my final comments....

The aluminum foil, as handled in the field, will provide unknown
contaminants and the contamination will not be consistent from sample to
sample. It can damage the fragile samples easily and will create a Peltier
Effect as well as galvanic corrosion immediately upon contact with any other
metal. Hopefully it will be the "weaker" metal and take the brunt of the
corrosion! But with CAI's and such???
The plastic bags, will have a more consistent level of contamination and be
relatively consistent from bag to bag in the same lot. They will not have
any of the effects of electrical corrosion mentioned above because of their
insulation properties of DC currents. And they are friendly to the sample
contained within as opposed to crinkled up aluminum.
In this case, it had rained and the dew on everything was major. Many
samples found in parking lots! So, all we could possibly do is reduce
further contamination of the human kind.
The best protection I saw in the field is where we double bagged a sample,
never touching it and then placed it in a large soft cloth.

Just my 5 cents!

Cheers!

Jim


Jim Wooddell
http://k7wfr.us



----- Original Message -----
From: "Carl Agee" <agee at unm.edu>
To: "meteoritelist meteoritelist" <meteorite-list at meteoritecentral.com>
Sent: Monday, April 30, 2012 6:34 AM
Subject: [meteorite-list] Curation of meteorites containing organics


>I just saw Jim Wooddell's post about aluminum foil and the new CM
> fall. It turns out that aluminum foil does react somewhat with
> carbonaceous chondrite. Apparently the recommended storage material is
> Teflon. This is what is used in NASA's Lunar Lab (Teflon bags and
> gloves). Cold and dry (nitrogen) storage are recommended too although
> if this meteorite has been sitting in the rain, then it may be moot.
> Take a look at Chris Herd's presentation of lesson's learned from
> Tagish Lake and Buzzard Coulee:
>
> www.lpi.usra.edu/meetings/sssr2011/presentations/herd.pdf
>
> --
> Carl B. Agee
> Director and Curator, Institute of Meteoritics
> Professor, Earth and Planetary Sciences
> MSC03 2050
> University of New Mexico
> Albuquerque NM 87131-1126
>
> Tel: (505) 750-7172
> Fax: (505) 277-3577
> Email: agee at unm.edu
> http://meteorite.unm.edu/people/carl_agee/
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Received on Mon 30 Apr 2012 11:20:38 AM PDT