[meteorite-list] What weather!

From: Piper R.W. Hollier <piper_at_meteoritecentral.com>
Date: Thu Apr 22 10:23:43 2004
Message-ID: <5.1.0.14.2.20030301120727.023e5a30_at_pop.xs4all.nl>

Hi Dave and list,

The meteorite weathering grade scale W0-W6 now commonly used was first
described by F. Wlotzka of the Department of Cosmochemistry at the Max
Planck Institute in Mainz, Germany in a short article "A Weathering Scale
for Common Chondrites" published in Meteoritics, July 1993. This article is
available online in NASA's ADS database:

http://adsabs.harvard.edu/abstract_service.html

Here is Wlotzka's short description of the weathering grades:

W0 -no visible oxidation of metal or sulfide but a limonitic staining may
be noticeable in transmitted light. Fresh falls are usually of this grade,
although some are already W1.
W1 - minor oxide rims around metal and troilite and minor oxide veins.
W2 - moderate oxidation of metal, about 20-60% being affected.
W3 - heavy oxidation of metal and troilite, 60-95% being replaced.
W4 - complete (>95%) oxidation of metal and troilite, but no alteration of
silicates.
W5 - beginning alteration of mafic silicates, mainly along cracks.
W6 - massive replacement of silicates by clay minerals and oxides.

Best wishes to all,

Piper Hollier
Amsterdam NL
Received on Sat 01 Mar 2003 06:18:37 AM PST