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

Michael Murray mmurray at montrose.net
Mon Sep 28 20:46:14 EDT 2009 

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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