[meteorite-list] golden iron color and Widmanstätten" patterns

From: cdtucson at cox.net <*cdtucson_at_meteoritecentral.com*> Date: Thu, 1 Apr 2010 23:55:16 -0400 Message-ID: <20100401235516.7NFK7.311617.imail_at_fed1rmwml32> · cdtucson_at_meteoritecentral.com

--
Carl or Debbie Esparza
Meteoritemax
---- Jason Utas <meteoritekid at gmail.com> wrote: 
> Carl,
> 
> > Nice try but, it seems obvious that you have no idea how classifications work.
> > If you recall in a recent post by Bernd. It was made perfectly clear that what determines a class has more to do with the O-isotopes than the actual lithology or chemistry of the rock.
> 
> Of a rock, yes.  This is an iron.  Irons are classified chemically,
> generally by irradiating a small sample and then counting the emitted
> particles.
> 
> So, no, you're wrong.
> 
> > Having cleared that up it does leave open the possibility that this is a Winonaite or a meso or pallesite for that matter.
> 
> Except for the fact that there are no visible silicates or olivine
> crystals.  It's either a mesosiderite that's made of pure nickel-iron
> or a pallasite that's the same (as I said in my message above, in case
> you didn't read it to the end).  But take a look at Seymchan.  A IIE
> iron.  A pallasite without olivine crystals is an iron meteorite.  And
> a mesosiderite without silicates would be classified as an iron
> meteorite as well, though  it would probably be classified as
> anomalous or ungrouped.
> 
> > The only way to be sure is to have it classified. And have the O-isotopes checked in order to plot against other meteorites .
> 
> If it were a stony meteorite, yes.  It's not.  You're assuming that a
> solid 6kg mass of nickel-iron displaying an obvious widmanstatten
> pattern is a primitive achondrite or stony-iron meteorite.
> 
> I'm not the one making ridiculous claims.
> 
> > But please don't belittle peoples guesses with false facts.
> 
> Everything I said was based on the observation of clear photographs
> and a knowledge of meteorite classes and textures.  If you have a
> problem with any of my observations, please tell me which ones were
> wrong.
> 
> Tell me any reason you might have for claiming that an iron meteorite
> that displays characteristics strikingly similar to classified and
> approved iron meteorites is an exceedingly rare and different type of
> meteorite that looks nothing like the provided photos.
> 
> I really don't know what to say.  Get it analyzed.  I bet you $100
> it's a typical octahedrite.  Make it $1000.  I know my irons.
> 
> > I'm sorry but, it has been established that Winonaites can have very little or a lot of metal and there is no rule that says that the silicates have to be recognized by Jason in order to be there.
> 
> Well, we have a few problems here.
> 
> 1) All of these metal-rich winonaites are the same meteorite as NWA
> 2680, a silicated iron meteorite.  They're paired.
> 2) Many IAB irons are isotopically identical to IAB iron meteorites.
> Classified, accepted, IAB irons.  Meteorites that have no silicates.
> 
> To be frank, it seems as though you misread Bernd's original post.  If
> you reread it, you'll see that this is the case, and the defining
> feature between IAB's and winonaites isn't oxygen isotopes -- because
> these two types are believed to come from the same parent body.  The
> difference between the classes lies primarily in their differing CRE's
> (that's cosmic ray-exposure ages, fyi).  In other words, the
> meteorites (IAB's and winonaites) might be chemically and isotopically
> indistinguishable.
> 
> This is where real problems arise.
> 
> In *no* other case do you have meteorites being classed based on CRE
> data.  Almost every meteorite that falls has a different CRE age,
> ranging from thousands of years (Kalahari lunars) to billions (many
> examples).  If you look at L6's, the range is enormous.  But they're
> chemically generally similar, isotopically, similar, and are grouped
> together.
> 
> IAB's silicate inclusions and winonaites are chemically
> indistinguishable from each other, and the only real difference
> between the two lies in their CRE ages.
> 
> They're the same stuff.
> 
> On to problem number three.
> 
> Winonaites are typically, for all intensive purposes, stony
> meteorites.  The only possible exception is NWA 2680.
> So the only example you have of a metal-rich winonaite has been
> classified by one of the world's most renowned experts on iron
> meteorites as an iron, and by several other experts -- in analyzing
> stony meteorites -- as a winonaite.
> 
> And you're tossing around the analyses by the folks who specialize in
> stony meteorites as the word of god itself.
> 
> Problem number four.
> Iron meteorites are rare.
> Winonaites are significantly more rare.
> Based on statistics alone, and it's appearance, this thing is probably an iron.
> But - there's only one "metal-rich winonaite."
> 
> So you're saying that this thing, whatever it is, is more likely to be
> the same class as a unique meteorite, than it is to be any other sort
> of iron.
> 
> When it looks like an iron.
> 
> Honestly...I don't have anything to say to that.
> 
> >They may be hiding under the metal. The point is that this has a very unusual look and it helps all of us learn by thinking about it. And it's fun.
> 
> And you're bashing me for assuming things?  When you're imagining
> invisible inclusions under the surface?  I'm sorry for ruining your
> fun guesses, but a question was asked and instead of just hazarding a
> loose guess, I made some observations and applied what I know to come
> to a conclusion.
> 
> Could it be a mesosiderite or a winonaite?  I suppose that, yes, this
> could be a startlingly unique new mesosiderite composed of a metal
> shell surrounding a silicate-rich interior.  Or a winonaite with a
> similar structure.  Your guess *could* be correct.
> 
> It's probably an iron, though.
> 
> > I think you saying; ?[It's a pretty coating of desert varnish on a (probably naturally) sandblasted iron.] ?is a bit of an oxymoron. How can it have desert varnish if it is wind blown and sand blasted?
> 
> You should look into things before you speak.
> 
> From wikipedia:
> 
> Originally scientists thought that the varnish was made from
> substances drawn out of the rocks it coats.[3] Microscopic and
> microchemical observations, however, show that a major part of varnish
> is clay, which could only arrive by wind.[4] Clay, then, acts as a
> substrate to catch additional substances that chemically react
> together when the rock reaches high temperatures in the desert sun.
> Wetting by dew is also important in the process.[2]
> 
> 
> > Nobody cares who is right here. they are just asking questions and trying to get answers. Your guesses may turn out to be right but, you cannot know that quite yet.
> 
> I'd be willing to bet on it.
> 
> > Playing the odds, I like what Bernd thinks.
> 
> Bernd mentions molten schreibersite.  Based on the sharp contours of
> the two larger regmaglypts in the wider-viewing photos, I think it's
> fairly safe to say that this iron has been substantially weathered,
> and that the original molten surface has long since been removed.  The
> presence of polished iron shale on the protected areas in regmaglypts
> also suggests a significant amount of surface removal; not only was
> the iron at one point buried (or at least bottom-up), but that amount
> of shale  was removed from its surface via abrasion as well.  You're
> looking at what used to be a thick, uniform rind of oxides there.
> 
> It could well be that phosphides in the iron naturally created its
> golden hue as opposed the the darker brown naturally polished irons
> that I posted photos of in my last email.
> But...the problem with that theory is that you need to have a
> phosphide rich iron that lacks any visible schreibersite (iron
> phosphide) inclusions, since there are *none* visible in the photos.
> Again, the fact that we have a cleanly wind-polished surface does
> wonders for us here; compare the following photos:
> 
> 1)  http://picasaweb.google.com/MeteoriteKid/Irons#5419302533230615154
> 
> 2)  http://picasaweb.google.com/MeteoriteKid/Irons#5444617699846214098
> 
> #1 is weathered, and while the cut side actually bisects a
> schreibersite inclusion right there on the edge of it, there's
> practically no sign of it on the meteorite's surface.
> 
> #2 - that sharply defined feature in the middle is schreibersite.
> There are two reasons for why it's so clearly defined.
> 1) It melts at a lower temperature than FeNi.
> 2) It weathers more easily as well.
> 
> Take a look at the photos of this golden 6kg iron again.  No
> schreibersites.  Probably not that much phosphide.
> 
> > So, rather than end your opinion with a "conclusion" , ?why not end it with a question mark like other (nice) ?people do?
> 
> Because the other suggestions were misleading.  Telling people that it
> could me a mesosiderite doesn't make any sense when it looks nothing
> like one.  Same goes for winonaite.
> 
> 
> You might as well post photos of a eucrite and tell people it's a lunar.
> 
> - It only works for April Fool's day.
> 
> Hm.
> 
> Touch?.
> 
> Jason
> 
> 
> > Carl
> > --
> > Carl or Debbie Esparza
> > Meteoritemax
> >
> >
> > ---- Jason Utas <meteoritekid at gmail.com> wrote:
> >> Hello All,
> >>
> >> It's a pretty coating of desert varnish on a (probably naturally)
> >> sandblasted iron.
> >>
> >> A winonaite would look like a stony meteorite. ?If it were a
> >> "metal-rich winonaite," you might as well call it a silicated iron -
> >> but there are no silicates visible anywhere on its (supposedly wind-)
> >> polished surface, so it's not a winonaite, that much is obvious.
> >> The fact that you can see a widmanstatten pattern on the sandblasted
> >> surface means that we're not looking at a lump of troilite, and the
> >> suggestion that the coloration could be due to iron sulfide
> >> is...strange. ?Troilite occurs as inclusions within iron meteorites,
> >> and it's clear that the sandblasted surface exhibits no such
> >> inclusions. ?Don't get me wrong - I see why you might say that, Mike,
> >> since troilite is a bronze-gold color as well, but...there's none
> >> there.
> >>
> >> So -
> >>
> >> The coloration is due to a thin layer of desert-varnish-related iron
> >> oxide that forms on the surface of irons exposed to abrasive desert
> >> winds (and not your typical temperate or tropical oxidation).
> >>
> >> See here for other examples:
> >>
> >>
> >> http://picasaweb.google.com/MeteoriteKid/Irons#5444617684310649778
> >>
> >>
> >> http://www.flickr.com/photos/cameteoritefinder/2336572790/
> >>
> >>
> >> But note that both of these irons are fresh; where fusion crust has
> >> spalled off, discolored, wind-polished iron is exposed below the
> >> surface.
> >>
> >> Many NWA 5549 fragments actually display similar surfaces:
> >>
> >>
> >> http://www.encyclopedia-of-meteorites.com/test/49248_8446_2637.jpg
> >>
> >>
> >> Aziz's iron looks significantly older, and, as you can see from the
> >> patches of iron oxide covering lower, protected areas on the polished
> >> surfaces, it was at one point completely covered in a rind of oxide.
> >>
> >> Again, the complete and utter lack of visible silicate inclusions
> >> rules out the remotest possibility that it's some sort of a stony iron
> >> meteorite (with the very vague possibility of its being analogous to
> >> something like a Brenham or Seymchan pallasite, but those are
> >> indistinguishable from other iron meteorites, so...it would still be
> >> an "ordinary" iron).
> >>
> >> Conclusion:
> >>
> >> The once-complete rind of oxide tells us that this is an old iron that
> >> was at some point buried, or at least was fluvially moved or exposed,
> >> at which point the upper half of its surface was exposed to arid,
> >> abrasive conditions.
> >>
> >> It's what appears to be a medium octahedrite from the definition of
> >> the widmanstatten patter on its surface (large, straight,
> >> clearly-defined kamacite boundaries rule out coarse or coarsest (see
> >> Ziz, a coarse octahedrite, for comparison - the grain boundaries are
> >> visible, but all you see are amorphous-shaped outlines and a general
> >> orientation due to schreibersite crystals and weathering on a few
> >> fragments), though this iron could conceivably be a fine octahedrite).
> >>
> >> Regards,
> >> Jason
> >>
> >> On Thu, Apr 1, 2010 at 2:21 AM, habibi abdelaziz <azizhabibi at yahoo.com> wrote:
> >> > hey all
> >> >
> >> > got some? time now and i? missed meteorite, sorry if i miss any emails or didn't answer;;
> >> >
> >> > ok many collectors ask me why? this iron has this golden color,
> >> > what is the process , that make it looking like that.
> >> > and why the?Widmanst?tten" patterns is showing on the surface,
> >> > http://www.flickr.com/photos/azizhabibi/page3/
> >> > can someone answer please ,as myself i do not know why its golden color,
> >> > i know i have sold two small cut iron that was looking like gold, i may have photo in my archives.
> >> >
> >> > thanks
> >> > aziz habibi
> >> >
> >> > ?habibi aziz
> >> > box 70 erfoud 52200 morroco
> >> > phone. 21235576145
> >> > fax.21235576170</font>
> >> >
> >> >
> >> >
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