[meteorite-list] Meteorite Question

From: Rhett Bourland <rbourlan_at_meteoritecentral.com>
Date: Thu Apr 22 10:00:06 2004
Message-ID: <IOEBKAHMGFBDJMOFGDFNKEGBDNAA.rbourlan_at_evansville.net>

Hello Pierre, Bernd, and list,
The statement that Burnwell is anomolous is based on much more than just its
low fayalite value.
Looking at pyroxene, olivine, iron, nickel, and numerous other values you
will see that Burnwell is much more reduced than normal H chondrites.
Understandably, type 3's should be thrown out (in this case anyway) as well
as weathered pieces but Burnwell is EXTREMELY fresh and is a type four. The
possibility that an unusual sample of this meteorite was used for
measurements is unlikely. If you've ever seen any of Burnwell in person you
could see that there's really nothing different in one area from another.
Its got a grey matrix with quite a few tiny chondrules (some armoured) in it
and at least in the piece I've got I haven't seen any shock veining (its
only a S3) or brecciation. Also, the methods used to classify it were the
same methods that the Smithsonian uses to classify all of its meteorites and
I don't think they make too many mistakes.
Best wishes,
Rhett Bourland
www.asteroidmodels.com
www.asteroidmodels.com/personal
www.meteoritecollectors.org

-----Original Message-----
From: rochette [mailto:rochette_at_cerege.fr]
Sent: Saturday, July 13, 2002 9:23 AM
To: Meteorite List; rbourlan_at_evansville.net; Bernd Pauli HD
Subject: Re: [meteorite-list] Meteorite Question


Dear Rhett,Bernd and list

In general when obtaining a measurement outside the norm (here Fa% for H
within 17-20), the inference "this is an anomalous meteorite" should not
be put forward before answering the questions:

-does the norm apply to this case? (obviously not for type 3 which by
definition show a large range in Fa%, with an average showing a standard
deviation of several %)
-then is there systematic bias? (possible for weathered finds, oxidation of
olivine starts by turning Fe to rust therefore decreasing Fa%)
-is the Fa% measurement well calibrated and what is the error bar? (It is
really difficult to get absolute precision below half a percent for this
parameter)
-is the studied sample representative?
-is the meteorite correctly classified? (possible case of Oviedo which may
turn to be an L)

excluding type 3, finds and incompletely classified meteorites and allowing
for a half percent error leave practically no anomalies in Bernd's list!
By the way why is Burnwell not fully classified?


Pierre
Received on Sat 13 Jul 2002 06:37:07 PM PDT