[meteorite-list] Flow lines on the INSIDE! Not. (cleaning irons follow-up)

From: Michael Murray <mmurray_at_meteoritecentral.com>
Date: Mon, 28 Sep 2009 18:46:14 -0600
Message-ID: <72929843-2CE7-4075-90BA-8ACF3292F84A_at_montrose.net>

Hi All,
I put my little suspect iron in a solution of water and calcium
carbonate. I actually wrapped it loosely with tinfoil and sat that
down in the mixture. I got out my trusty battery charger and
connected the red lead to a sacrificial piece of junk strap metal and
sat that down along one side of the plastic bowl. I connected the
black lead to the tinfoil. Actually clamping it against the side of
the bowl same as I did the piece of strap on the other side of the
bowl. Anyway, I poured in a couple teaspoons cleanser and swished it
around with a plastic spoon so it was dissolved good. Plugged in the
charger and watched as a steady stream of bubbles headed from the
tinfoil towards the sacrificial anode strap. After about two hours of
cooking, I can now see what I have. A really sculptured, bright
chrome something that is as hard or harder than tool steel (don't ask
how I know that last bit) and shaped like a stretched out version of
Willamette. I did a nickel test and think now with all I see that it
might need to go to someone to get checked further if I want to know
for sure. Anyway, the process worked better than I was expecting.
Doesn't seem to be dangerous to do. I put the charger on 12V, 6 amp
scale. I left the solution outside when it was cooking. I treated
my specimen to a bath in penetrating oil when I had finished cleaning
it. One more interesting tidbit, looks like after the red rust was
removed, left on the suspect rock is a very thin black coating in
quite a few places, mostly in the low spots. If that is magnetite
then I answered my own question, no, the process doesn't remove the
oxide, only the red rust. My little experiment worked well enough for
my purposes, but hopefully no one with a stone of any value will
follow my lead. I would hate to think I inspired someone to ruin a
valuable specimen.

Mike in CO



On Sep 28, 2009, at 1:52 PM, countdeiro at earthlink.net wrote:

> Hi Jason, Piper, Mike and List,
>
> Gathering my tattered cloak up to cover myself, I must say that even
> I, with less than a year in the game, wouldn't be so ignorant as to
> say I saw flow lines on the INSIDE of a specimen. What I said.. and
> did see.. were..and I will be a bit more descriptive here...nearly
> parallel, but sinuous, thin, rounded, iron lines orientated in one
> direction on the outside surface of a formerly concreted and rusted
> Nantan that I had blasted the crap out of and wirebrushed. It looks
> lovely. Maybe I should put it eBay and call it a 100% crusted and
> oriented individual...:o}
>
> Guido
>
> -----Original Message-----
>> From: Jason Utas <meteoritekid at gmail.com>
>> Sent: Sep 28, 2009 4:45 AM
>> To: Meteorite-list <meteorite-list at meteoritecentral.com>
>> Subject: Re: [meteorite-list] "flow lines" on weathered irons (was
>> "question on cleaning irons")
>>
>> Hello Piper,
>> Of course - hence the differential weathering rates of Campos ("old"
>> versus "new"), to name one of many examples.
>> Perhaps the best example of such weathering can be seen on irons from
>> Gibeon. I unfortunately don't have a copy of Buchwald here, but if
>> anyone does have access to the second volume, if they could flip
>> through the Gibeon section, they would find a photograph of a
>> beautiful mass of Gibeon (I forget the name of the mass) on display
>> in
>> a museum in Germany. It displays beautiful fusion crust and
>> smooth-edged, shallow regmaglypts - it looks as fresh as many
>> Sikhotes
>> on the market today. Compare it to many of the larger Gibeons on
>> ebay
>> today and you'll see little-to-no resemblance. If anyone out there
>> can scan a picture of said page, I'd be much obliged. It really is a
>> good example.
>> There are, however, a few common irons which I would never expect to
>> have fusion crust: Canyon Diablo, Toluca, Odessa, and Nantan, to name
>> a few. I've seen hundreds, if not thousands of examples of each, and
>> I have never seen a single one of any of them that came close to
>> being
>> "fresh" enough to retain a trace of fusion crust.
>> Nantan is one of the most corroded and least stable iron meteorites I
>> have ever known, though Dronino's turning out to be about as bad.
>> People need to learn more in order to clear up the misconception that
>> all meteorites show signs of a hot, violent entry through the
>> atmosphere; I see NWA's on ebay all the time that are nothing but old
>> weathered fragments coated with desert varnish. Check out this
>> seller:
>>
>> http://myworld.ebay.com/eegooblago/
>>
>> Almost all of his stones are covered in a 'glossy fusion crust.' Oh
>> wait - those are just desert varnished fragments that have been
>> weathered to hell. Most of the melt features the seller notes are
>> due
>> to sandblasting and corrosion, and s/he goes so far as to say that
>> the
>> cracks in his stones formed when they hit the ground! Anyone
>> remotely
>> familiar with meteorites and weathering processes knows that over
>> thousands of years, meteorites fracture and break apart, in a manner
>> completely unrelated to their having impacted the Earth.
>> This seems like a very similar misconception; Guido even notes
>> finding
>> flow lines on the inside of the meteorite, having broken it open.
>> There's no way there would have been any flow lines on the surface of
>> the iron, never mind the inside of it. It simply isn't possible.
>> Regards,
>> Jason
>>
>> On Mon, Sep 28, 2009 at 12:47 AM, Piper R.W. Hollier
>> <piper at xs4all.nl> wrote:
>>> Hi Guido, Jason, Mike, and list,
>>>
>>> At 22:33 27-09-09, Jason wrote:
>>>>
>>>> Regardless of how well you cleaned your Nantan, whatever you found
>>>> under the surface was not flow lines.
>>>
>>> It appears that the layers of taenite and kamacite do not always
>>> oxidize at
>>> the same rate at the surface of a buried iron. This would make sense
>>> intuitively, since the proportion of nickel is different. Just as
>>> nitol has
>>> a differential effect on taenite and kamacite in the lab, some
>>> conditions of
>>> soil chemistry might produce an analogous result in the strewn
>>> field, albeit
>>> much more slowly. What is sometimes left after a long period of
>>> weathering
>>> is a pattern of parallel grooves on the outer surface that might be
>>> (mis)interpreted as flow lines.
>>>
>>> This is an effect that I first noticed on a thick slice of Toluca
>>> from Alain
>>> Carion's collection that was on display at a wonderful exhibition
>>> at the
>>> Ecole des Mines in Paris in 1998. The correspondence between the
>>> shallow
>>> ridges on the oxidized edge of the slice and the Widmanstaetten
>>> pattern of
>>> the cut surface was rather obvious.
>>>
>>> There might be something about the specific soil chemistry at the
>>> site that
>>> could make this effect more pronounced at some localities (e.g.
>>> Nantan or
>>> Toluca) by enhancing the difference in oxidation rate.
>>>
>>> Piper
>>>
>>> ______________________________________________
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Received on Mon 28 Sep 2009 08:46:14 PM PDT