[meteorite-list] Fusion crust vs desert varnish?

From: John Gwilliam <jkg_at_meteoritecentral.com>
Date: Thu Apr 22 10:17:43 2004
Message-ID: <4.2.0.58.20031210091818.009e1de0_at_mail.theriver.com>

JD,
Many of the meteorites found in desert environments have been subjected to
"sand blasting" for many years. This can alter the fusion crust to
different degrees depending on time and conditions. I've seen many
meteorites from the NWA region that have had most if not all of the fusion
crust removed by the erosive effects of wind and sand. Others have just
been polished by this effect and still have some fusion crust remaining
even though the surface may be shiny as you mentioned.

  Desert varnish can also make it hard to make an accurate determination
about the amount of remaining fusion crust. The only way I know of is to
cut a window that is at or near a right angle to an uncut surface of the
meteorite. A close look under magnification will show whether or not there
is any fusion crust there.

Best,

John Gwilliam

At 10:42 AM 12/10/03 -0500, jcowsar_at_pol.net wrote:
> When I look at some of photos of the hot desert NWA meteorite Ebay
>auctions, I can't tell if the nice looking blackish brown coating on the
>individual meteorites is fusion crust or just desert varnish with
>probably little or no fusion crust remaining. Advice please on helping
>this novice collector determine the difference. Shiny appearance =
>desert varnish?
>
>thanks,
>
>jd cowsar
>
>
>
>
>
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Received on Wed 10 Dec 2003 11:28:42 AM PST