[meteorite-list] Desert varnish

From: Matt <Matt_at_meteoritecentral.com>
Date: Thu Apr 22 09:50:23 2004
Message-ID: <00e301c1dce9$514658e0$8fbf7fa5_at_D7220234W2K>

Here is the definition from the American Geological Institute Dictionary:

desert varnish
A thin dark shiny film or coating, composed of iron oxide accompanied by
traces of manganese oxide and silica, formed on the surfaces of pebbles,
boulders, and other rock fragments in desert regions after long exposure, as
well as on ledges and other rock outcrops. It is believed to be caused by
exudation of mineralized solutions from within and deposition by evaporation
on the surface. A similar appearance produced by wind abrasion is properly
known as desert polish. Syn: desert patina; desert lacquer; desert crust;
desert rind; varnish.
----- Original Message -----
From: <ajones_at_siliconspace.com>
To: <meteorite-list_at_meteoritecentral.com>
Sent: Friday, April 05, 2002 2:28 PM
Subject: [meteorite-list] Desert varnish


> Greetings everyone!
>
> I was recently doing a bit of research on desert varnish on boulders &
> meteorites and found this information regarding a possible organic origin:
>
> ['... desert varnish is formed by colonies of microscopis bacteria living
> on the rock surface for thousands of years' (Ronald Dorn and Theodore
> Oberlander - Science, Volume 213, 1981)]
>
> I was curious as to whether this theory has wide-spread belief.
>
> Also, is it believed that meteoritic desert varnish is caused by the same
> process as terrestial rock desert varnish?
>
> Regards Art
>
>
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Received on Fri 05 Apr 2002 04:31:58 PM PST