[meteorite-list] re: weathering grades

From: marco.langbroek_at_wanadoo.nl <marco.langbroek_at_meteoritecentral.com>
Date: Thu Apr 22 10:01:30 2004
Message-ID: <1023113469.3cfb78fd3ff8c_at_webmail3.wanadoo.nl>

> In my searches of Holbrook, I have found pieces that
> are near to pristine, and others just yards away from
> those that are weathered to the point of being nearly
> unrecognizable.

Archaeologists like me are well accustomed to large differences in weathering
grade of stone artifacts. If have done quite some refitting with Old Stone Age
artefacts from Middle Pleistocene sediments. Refitting means that you glue
together shards of stones that once were knocked off from one stone nucleus by
our ancestors. Pieces from one of the same nucleus, found only a few yards from
each other, indeed sometimes even pieces from one and the same anciently broken
artifact, sometimes can show a very large difference in patina. This is most
probably due to very local differences in soil conditions, e.g. soil accidity,
etc. I have a few flint artifacts here where you can see the clear results of
differential weathering on one and the same piece due to plant root etching.
While meteorites are not flint, I do think similar phenomena take place which
explains why some pieces from a strewnfield can appear fresh while others are
strongly weathered. Simple things like the nearby presence of a bushel of grass
or a shrub, or a mole pipe already can make for a difference compared to piecs
lying in barren sediment.

Marco Langbroek
Received on Mon 03 Jun 2002 10:11:09 AM PDT