[meteorite-list] Update: Franconia area meteorite classifications
From: Ruben Garcia <meteoritemall_at_meteoritecentral.com>
Date: Sat Jul 24 14:49:30 2004
Franconia area meteorite classification update.
Its been nearly eight months since Mike Miller and I
delivered our first batch of Franconia area meteorites
to Arizona State University for classification.
Originally we along with those at ASU separated our
finds (all of which were windowed) into eight
different piles. They were separated mostly on this
criteria, (1) number and definition of chondrules,
(2) amount of metal and metal distribution, (3)
weathering and overall exterior appearance. When
finished each individual pile consisted of similar
looking meteorites, some piles had low metal while
others had literal veins of iron. Visible chondrules
in each pile of meteorites ranged drastically too. One
pile of meteorites had brilliant and well-defined
chondrules while another pile had almost no chondrules
at all. This process of selecting meteorites for
classification went on for several weeks, each time
selecting one representative sample from each pile for
classification. Eventually we left over 20 samples to
be classified and studied.
To date half of all the samples we left with Arizona
State University have been classified.
I must admit that I for one was surprised at the
finding. Of the first eight Franconia area meteorites
we had classified each one has come back with the same
H-5 classification. The only real difference in some
of the classified specimens was the weathering, which
ranged from 1-3. However, weathering is not much of a
factor since we don’t know where each meteorite
originally landed, in other words one may have landed
in a dry area and another in a puddle.
This means that more than likely each of those eight
meteorites will pair with the original Franconia
meteorite that John Wolf found. However, these are
still being studied and I suppose it is possible that
subtle differences may distinguish one or more of them
from the original H-5 Franconia meteorite…. but, it is
doubtful. All the data is certainly pointing towards
these eight being Franconia.
Obviously Arizona State University has more work to do
regarding the classifications of the remainder of the
specimens. It does look as though some unique
meteorites will come from the area, at least one L and
one or more H chondrites. However, these will more
than likely be lone specimens rather than many. The
Franconia area irons that many collectors are so
interested in have not yet been studied and may prove
to be very interesting. We have personally witnessed
beautiful 20 gram-50 gram irons found in the area.
Were these small iron meteorites born from within a
larger Franconia chondrite with nickel iron veins? No
one yet knows. We'll try and keep the "Meteorite List"
informed as we know more.
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Received on Sat 24 Jul 2004 02:49:27 PM PDT