[meteorite-list] Fusion Crust on Irons

From: Gary K. Foote <gary_at_meteoritecentral.com>
Date: Mon, 04 Dec 2006 16:00:34 -0500
Message-ID: <45744622.30282.26AD618_at_localhost>

I have a number of sikhotes that have that nice blue sheen. Beautiful for sure.

Gary

On 4 Dec 2006 at 12:10, Dave Freeman mjwy wrote:

>
> Get a fresh looking blue tinted shikote alin, now that is a fushion crust, about .0008
> thick but still a fine crust of blue steel. Dave F
>
> Gary K. Foote wrote:
> Thanks for clearing that up Doug. I've always felt a bit dumb talking about fusion
> crust and irons.
>
> Gary
>
> On 4 Dec 2006 at 13:59, MexicoDoug wrote:
>
>
> Hi Gary,
>
> Fusion crust can be in the eyes of the beholder, so the difficulty with this
> question is we are making a one-size fits all definition.
>
> For the irons, you could get a verrrry thin local destruction of any
> crystalline patterns or figures (no longer etch), some chemical change from
> 'burning' up including colors. In the case of stones, it is a different and
> typically a glazed-silicate ceramic crust forms. It can get a rainbowish
> tint from burnishing, though it usually looks somewhat bluish. It's so thin
> that it quickly is lost to other mineralization in the oxidizing humid
> environment that is earth's.
>
> So there is a difference. But loosely thay can all be attributed to
> 'fusion' though in the case of iron it has a different characteristic. In
> either case, when the fusion crust is black, this is generally caused by
> oxidized iron during the entry, not terrestrialization. That is a main
> difference between what we see on many older irons in dry and stable
> environments.
>
> So, yes, irons can have a fusion crust, it is just not predominantly a
> ceramic kiln glaze best seen from some achondrites, which is the classic...
>
> Best wishes, Doug
>
>
> ----- Original Message -----
> From: "Gary K. Foote" <gary at webbers.com>
> To: <Meteorite-list at meteoritecentral.com>
> Sent: Monday, December 04, 2006 1:26 PM
> Subject: [meteorite-list] Fusion Crust on Irons
>
>
>
> Hi All,
>
> Recently I have read a few posts to this list that definitively claim that
> irons do not form a fusion crust. Yet, in Norton's "Rocks From Space",
> [pg 167 in my softbound edition] it clearly states the following;
>
> "Iron meteorites have the thinnest crust of all, usually only a small
> fraction of a millimeter thick. A fresh crust is blue-black to black and
> looks like freshly welded steel. This crust is fragile and easily
> destroyed if the meteorite weathers for even a short time."
>
> So, which is true? Crust or no crust for irons?
>
> Gary Foote
> http://www.meteorite-dealers.com
>
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Received on Mon 04 Dec 2006 04:00:34 PM PST