[meteorite-list] Fusion Crust on Irons--Not

From: Martin Altmann <altmann_at_meteoritecentral.com>
Date: Thu, 19 Nov 2009 13:21:01 +0100
Message-ID: <000d01ca6912$c27e5ef0$07b22959_at_name86d88d87e2>

Unlike in politics and public opinion (and sometimes in science),
in meteoritics
it sometimes can be more difficult to adhere to theories/legends,
if one gets samples in ones very hands, which exhibit the opposite of that,
the theory postulates.

If you ever had an early picked Sikhote at hand,
or if you had taken from Andi Gren's Boguslavka slices
(a fall, who simply hadn't enough time in field, to develop a magnetite,
wuestite, limonite or whatever -ite weathering crust),
you would be very surprised.

Cause they don't display that ominous blue-ish flimsy luster, which is often
reported as fusion crust,

but a thick and fat layer of a discernibly different matter than the
material beneath, of a dark colour and rough to silky surface.

I never believed in iron fusion crusts neither, but when I got in these
freshly picked up observed falls, I was disabused.

Main problem in that question is, as it was correctly mentioned here,
that we simply have so few pristine samples of fresh iron falls and that
most irons we get in our collections arrive with weathered or artificially
cleaned surfaces.

Now you may argue about the word "crust" as a (pseudo-)scientific term...
well for me scientific terms are best, when they keep most of their meaning
they have in their common use in the language.
And there crust - meanst for me a layer on the outside of an object.

.....and we have the problem, that there exist these freshly fallen lumps
with that strange crust. Shall we hide them in the deepest corner of our
drawers, cause they don't fit in the axiom, that fusion crusts are fusion
crusts only, when silicates are melting?

Sometimes, if the results don't fit into a theory, one has to think about
modifying the theory,

Else there wouldn't be no meteorites in our sense at all,
Nada, Niente, Nix, Nimic,
cause we all would know that they are products of our Aristotelian
atmosphere, solified accumulations of terrestrial vapours and probably
created by lightning strokes,
wouldn't we?

Best!
Martin


  

 



-----Urspr?ngliche Nachricht-----
Von: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von MEM
Gesendet: Donnerstag, 19. November 2009 04:31
An: Meteorites USA; metlist
Betreff: Re: [meteorite-list] Fusion Crust on Irons--Not

Stopping in a few minutes to state again that all this discussion about
fusion crust on irons is right next to unicorns postulations. Everyone says
that fusion crust on irons exists but no one can come up with the proof.
Non-silicate bearing irons DO NOT/CANNOT have FUSION crust: they have a very
fragile magentite micro-crystal "film" and they have an ablation surface
but, they can't by definition have a "fusion crust" and no matter whom the
expert quoted they still do not have a fusion crust. A fusion crust has to
have a silicate source to for the glass component of the crust-- Nada, Nix,
No How.

Both silicate and non-silicate meteorites have an ablated/ablation surface,
and they can show flight features--but not all meteorites have a fusion
crust. I have some OCs which have flow lines UNDER the fusion crust
remnants.

If anyone still defends the presence of fusion crust on (non-silicate
bearing) irons then show me the "crust"...can't?..ok show me the glass? ....
right then-- no photos, no thin sections, no micro graphs???......And while
there was one close up of an ablated surface showing soft wavy lines of
briefly melted metal that was aligned to aerodynamic vectors--This does not
fusion crust make.

Unlike in politics and public opinion, in science, no matter how often an
untruth is repeated it doesn't become "truth" by majority belief. But
science, being a human endeavor, sometimes can find itself "off track" and
when it does it accepts the error and gets back on track.

Elton
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Received on Thu 19 Nov 2009 07:21:01 AM PST