[meteorite-list] Rust Question about my stone meteorite.

From: Steve Schoner <schoner_at_meteoritecentral.com>
Date: Mon, 13 Sep 2010 16:58:36 GMT
Message-ID: <20100913.105836.22574.1_at_webmail11.dca.untd.com>

Re-post as I can never seem to get the subject right when posting from a "digest from the met-list)


---------- Original Message ----------
From: "Steve Schoner" <schoner at mybluelight.com>
To: meteorite-list at meteoritecentral.com
Subject: Re: Meteorite-list Digest, Vol 85, Issue 27
Date: Mon, 13 Sep 2010 16:53:12 GMT

Martin and all,

I too am worried about this trend, using BFK to "preserve" meteorites, especially stones.

Having moved out of meteorite hunting due to disability, over the last 8 years I have kept my interest alive by learning the thin section process, and how to make them economically.

What I have noticed is that some stones that have been "treated" can be extremely difficult to bond to glass. Any type of oil, or oxygen depleting substance will cause this, not to mention that it also changes the isotopic nature of the meteorite that will show up in micro-probe analysis.

A simple soak in pure alcohol will do no harm.

Also for some stones and irons, I have used alcohol and sodium hydroxide. One meteoriticist was adverse to this as he said that it would change isotopic nature. But I countered that in that if one looks at the reason for the rusting in irons or stones is the presence of chlorine that is derived from long term exposure to weather and soil. Chloriine from chlorides in the soil attach to pure iron as Ferric Chloride (FeCl3) which is highly hydroscopic, causing a ongoing catalytic reaction where it makes the iron latch onto oxygen thus turning the iron into rust. That is why one finds iron relics on dry lakes that are completely reduced to rust, and also the reason for the so called "Lawrencite" decay of meteorites.

A solution of 70% alcohol and sodium hydroxide (NaOH) turns that ferric chloride (Lawrencite) into salt (NaCl) because chlorine has a higher affinity to sodium than to iron. It then creates a brine solution leaving the rusted iron as ferrous hydroxide (Fe[OH[2). (Fe[OH]2) then turns into FeO2-3 upon drying which is plain rust. But before drying the meteorite must be soaked in distilled water which will remove any salt on the surface of in the cracks. Thus with chlorine removed, the ongoing rusting caused by catalytic hydroscopic and acidic FeCl3 stops, The only addition, if any, is a trace of salt caused by this process. And most weathered meteorites will have traces of terrestrial salt anyway. I doubted that sodium hydroxide and alcohol would remove other elements that are bound in meteorite minerals.

(Thechemical reaction is more complicated than what I have explained in the above paragraph. But simply stated the result is common table salt and solid stable rust. The chlorine has been removed from the meteorite. And I have done this with stones, such as Lamont, Kansas a terrible ruster.)

I think the meteoriticist saw my point with regards to this process, and that that additional salt could be excluded from a micro-probe analysis in the study of irons.

Anyway, that said, using oils or oxalic acid containing oils on stones is another thing. First off, oils are extremely difficult to remove from stone meteorites most of which are porous. Not only will they affect the thin section process, but also make classification as Martin has noted difficult if not impossible.

Steve Schoner
http://www.petroslides.com
IMCA #4470
   

Message: 8
Date: Mon, 13 Sep 2010 14:24:16 +0200
From: "Martin Altmann" <altmann at meteorite-martin.de>
Subject: Re: [meteorite-list] Rust Question about my stone meteorite.
        BKF is the best :)
To: <meteorite-list at meteoritecentral.com>
Message-ID: <001e01cb533e$957ebd20$c07c3760$_at_de>
Content-Type: text/plain; charset="iso-8859-1"

Humhem...please!

No offense. It's absolutely you're private affair, what you're doing with
your meteorites.

Though in general I think it's a big No-No to manipulate stony meteorites
that way, to artificially bleach them. (Just was looking, "Bar Keeper
Friend"s main reactive agent is oxalic acid).
Stone meteorites are no irons. In my opinion such a treatment will make them
to a certain degree worthless,
as they can't be used anymore for scientific measurements.

What I would urgently expect, is to avoid, that such bleached chondrites
would be brought in circulation.
The meteorite sector, other than the minerals and fossils sector, all in all
was so far relatively spared from manipulated or fudged specimens.

It would be in my very personal opinion everything else than good, that W2,
W3, W4 material now would be pimped to be suggestive of being a W0 or a W1.

I hope we all can agree about?
Worried
Martin


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Received on Mon 13 Sep 2010 12:58:36 PM PDT