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

[Greg Stanley]

Elton:

Take a look - the Smithsonian classifies the meteorites from Antarctica and some of the Irons are described as having a fusion crust.

Greg S.


http://curator.jsc.nasa.gov/antmet/samples/petdes.cfm?sample=MIL07666


Sample Number      MIL 07666
Pairing     MIL 07666
Newsletter     31,2
Location     Miller Range
Field Number     18159
Dimensions     5.0 x 2.9 x 1.4
Weight     96.25
Original Classification     Iron (IIAB)

Macroscopic Description - Cari Corrigan and Linda Welzenbach
This lozenge-shaped meteorite is flight oriented with a slight melt flange on the top side. The bottom or flight surface is finely pitted, the top side smoother but with sporadic, deeper regmaglypts. Fusion crust is 100% and exhibits mild oxidation in the form of iridescence and minor halos.

Thin Section Description - Tim McCoy, Cari Corrigan and Linda Welzenbach
The meteorite was examined from a cut and etched surface, which bisected one end or nose of the specimen. A thin fusion crust is preserved over most of the meteorite, and gradational heat alteration zone of approximately 1.0-2 mm thick underlies the fusion crust on the bottom or flight side, and is less than 0.3 mm thick on the top side. A prominent coarse a2 structure is found throughout. The section exhibits subequant grains ranging up to 1 mm in size which meet at 120° triple j





----------------------------------------
> Date: Wed, 18 Nov 2009 19:30:39 -0800
> From: mstreman53 at yahoo.com
> To: eric at meteoritesusa.com; meteorite-list at meteoritecentral.com
> Subject: 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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