[meteorite-list] Re: rust and crust

From: Steve Schoner <steve_schoner_at_meteoritecentral.com>
Date: Thu Apr 22 10:16:35 2004
Message-ID: <20030821182702.11658.qmail_at_web12706.mail.yahoo.com>

--- Stephen McMann <stephen_mcmann_at_hotmail.com> wrote:

---------------------------------

Dear List,

I thought that I would ask a question relating to the
never-ending rust thread. I hope that this has not
already been fully addressed. As a fairly new
collector I may not be familiar enough with the
archieves. Those who are tired of rust discussions
should not read this.

A large part of my collection consists of Sikhote
individuals. Of course one of the many things that
makes Sikhotes appealing is that they are usually
relatively stable. This combined with their abundence
makes it tempting to treat them carelessly. However,
I wish to err on the side of caution. I want mine to
be in good condition many years from now.

I have taken measures to inhibit the arrival of fresh
Cl- and moisture. They currently live in plexiglass
cubes with VCI paper and silica dessicant. Several
were wiped with a silicone gun cloth. However, I
aquired my SAs from a variety of sources and can say
little about their histories. I am sure that at least
some of them have been held in sweaty hands. One of
them (a fairly well oriented individual) is shedding
flakes, suggesting that it is sick.

Of course another characteristic of SAs is that
individuals are covered with a delicate crust whose
characteristics have been determined by some
combination of rapid passage through the atmosphere,
post-fall weathering in the field, and post-collection
treatment. Some crusts are black, rich in magnetite,
and often smooth or marked with flow lines. Other
crusts are more orange, rich in limonite, and can be
avariety of textures. I'll say that both kinds of
crusts can be interesting and attractive. On the
other hand I don't want a meteorite with a touch of
orange to turn into a ball of poo.

I have been intrigued by recent discussions about
stabilization treatments such as soaking meteorites in
alcohol and perhaps adding some NaOH to help remove
CL-.

Now the question.

Can anyone tell me what treatments are best for
stabilizing crusted meteorites? In particular, how
will NaOH affect the various kinds of crusts that you
can find on SAs?

Thank You

Stephen McMann


In my experience with NaOH, with distilled water and
alcohol, rusting does not occur and only the offending
chlorides are affected and neutralized. Mix according
to the stated method, and if you find that there is a
layer of brine at the bottom of the container, add
small amounts of distilled water till it goes back
into solution.

I have use NaOh with SA's several times and each came
out with good results.

Steve Schoner/ams


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Received on Thu 21 Aug 2003 02:27:02 PM PDT