[meteorite-list] Nickel free metal in Meteorites

From: cdtucson at cox.net <cdtucson_at_meteoritecentral.com>
Date: Fri, 26 Mar 2010 14:06:33 -0400
Message-ID: <20100326140633.UL8GK.46482.imail_at_fed1rmwml4201>

Jeff,
Thank you for your well explained points.
As I have said many times before, you would make an excellent teacher as your answers always stimulate more thoughts.
On that note. you acknowledge that nickel free metal does exist but, from reduced metal and is very small. With all due respect.
Isn't size a relative thing?
I mean looking at things on our scale the size of Nickel free metal in chondrules is small. So, doesn't this means it could be bigger?
Look no farther than our own planet. We are way different than other planets.
I have been told by Scientists that the earth is so diverse that it makes identification of meteorites difficult. This because Earth can and does have so many different types of rocks. And this is just one planet.
So, going back to scale. What if this Reducing of Fe O that turns it into nickel free iron happens to be really big? Say the scale more like Artares which makes Earth look like a grain of sand?
Based on our current method of weeding out meteorwrongs we may never know if really big reduction occurs because as part of the weeding process we eliminate all metal objects that do not contain nickel. And this reduction process as you say is a known fact.
I see more abstracts based on theory than on nickel free iron facts.
Another size scale dilemma is also acknowledged in meteorites. They say ( tongue in cheek) this is either a very large inclusion and the rest of the meteorite is missing. Or this is the whole thing. This is the case with irons. Sometimes the iron is nearly pure and other times it is mixed with silicates as in meso's. But again the point is that these small bits of nickel free iron could be big but we will never know.
It seems to me if we paid more attention to morphology and find location and less on nickel content (as a must) that we would discover an iron without nickel. Maybe not as big as Hoba but not as small as what was found in HAH 237 CBb either. I believe this nickel free iron was also found in one of the Kalahari Lunar's. Is that from a chondrule also?
This particular meteorite HAH 237 is the one they used recently to reset the date of our solar system but not important enough to open our eyes to the lack of nickel in bigger meteorites.
I don't get it?
I understand there is always a story. "This thing fell through the roof" Okay, does it look man made? Does it have serial numbers on it? Is it identifiable as an object of any kind like a piece of a tree shredder blade? If these answers are no then maybe just maybe it did fall from the sky? (NJ meteorite).
In this example it was determined to be possible space junk and yet nobody bothered to show which space object it could have come from. This object would have had a significant amount of not only monetary value but scientific as well. What was this stainless steel chunk of metal doing up in space?
Why would NASA have misplaced such a strange piece of stainless steel? The science was dropped but, it came from somewhere. We may never know from where though. We dropped the ball on NJ and we may be dropping balls every day from a lack of nickel. Heaven forbid we find the first large nickel free iron! Obviously it would be rare but, there are known ungrouped irons that are equally rare.
Just another question.
Carl

--
Carl or Debbie Esparza
Meteoritemax
---- Jeff Grossman <jgrossman at usgs.gov> wrote: 
> Ni-free metal occurs within chondrules that have experienced reduction 
> during melting.  These chondrules were originally mostly free of metal 
> and therefore free of Ni, but contained oxidized iron (FeO) in the 
> silicate minerals.  During reduction, the FeO was converted into Fe 
> metal (if the reducing agent was H2, then you'd also make H2O; if it was 
> C then you'd make CO/CO2).  The pure Fe metal that is made can manifest 
> itself as "dusty metal" grains within olivine crystals, or sometimes can 
> coalesce into larger Fe metal particles in the chondrule.
> 
> The thing about this is, it is a local effect within a few chondrules.  
> Most of the metal in the chondrite is still Ni-bearing.  There is no 
> easy way to make large masses of this pure Fe metal, such as would form 
> iron meteorites, because any process that would segregate metal, would 
> segregate all of it, not just these strange particles.
> 
> Jeff
> 
> On 2010-03-25 5:59 PM, cdtucson at cox.net wrote:
> > List,
> > During recent research into CBb chondrites I stumbled upon an article from 2007 with references from Rubin  that shows an image of a CC chondrite with nickel free metal.
> > How is this possible?
> > In past conversations with Scientists when I have asked why do iron meteorites always have to have nickel. The typical response is that they not only have to have nickel but, it has to have a few percent of nickel and not just PPM's of it. In explanation of this as I recall, I've always been told the reason  that meteoritic iron always has to have Nickel is because in nature there is no way to separate the two elements.
> > If that is true then how is it that in this case we do in fact have meteoritic metal without nickel? somehow they got separated.
> > Unless this analysis is wrong does this not teach us that yes in fact there can and does exist meteoritic iron devoid of nickel. And therefore there not only could be Iron meteorites without nickel but,this ups the odds that there in fact are meteorites without nickel.
> > Please see attached abstract. Back scattered images Figure 2 at the fifth page from the top of the article. It says;
> > "D. Close up of a CC Chondrule texture. Radiating unidentified minerals and Nickel free metal (met) are set up in a silica-rich matrix."
> >
> > http://www2.mnhn.fr/hdt205/leme/doc/2007%20Gounelle%20et%20al.%20EPSL.pdf
> >
> > Thanks Carl
> >
> > --
> > Carl or Debbie Esparza
> > Meteoritemax
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> 
> 
> -- 
> Dr. Jeffrey N. Grossman       phone: (703) 648-6184
> US Geological Survey          fax:   (703) 648-6383
> 954 National Center
> Reston, VA 20192, USA
> 
> 
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Received on Fri 26 Mar 2010 02:06:33 PM PDT