[meteorite-list] Zag classification, / - differences, pop quiz

From: Mikestockj_at_aol.com <Mikestockj_at_meteoritecentral.com>
Date: Fri Nov 12 12:59:38 2004
Message-ID: <ff.65d50f6.2ec653f1_at_aol.com>

In a message dated 11/12/2004 8:59:26 AM Mountain Standard Time,
meteorites_at_hotmail.com writes:
Strange...type Zag .....H3/6 very few difference.....and its brecciated from
the pieces have cut....

Hi Matteo and all
I want to point out that the correct classification of Zag is H3-6. Which
indicates a H3 and an H6 stuck together (aka brecciated). Just think of the
-(dash) as a comma or H3, H6. A H3/6 would be a transitional meteorite that
includes grades from H3 to H4 to H5 to H6. Think of the / (slash) as a line with an
arrow on both ends. In other words it is going from an H3<-/->H6. By the way
such a meteorite H3/6 would be virtually impossible to create due to the broad
range of metamorphic grades (think temperatures) involved. We do see some
meteorites classified transitional across three grades e.g. Shisr 010 L4/6 & NWA
537 LL4/6 though it is rarely used. It would be nice to see the research for
these meteorites and find out if these are truly transitional or if a simple
error as was made.
My suspicion is some of meteorites with two grades of separation are mixed
up. In other words some listed as transitional (/) are brecciated (-) and vice
versa. Though there is almost no way to know this without seeing the original
research. The nomenclature for the usage is a fairly recent ruling.
One caution is the classification is not meant to be all inclusive. Could we
not have a H3-5-7 or how about a L3/4-5-6/7? Current accepted practices use
only 2 numbers. It is not a simple black and white classification as most
collectors believe.
This leads me to caution any one who is buying a meteorite and trying to get
all the classification grades especially for the ordinary chondrites. We must
remember that the classification scheme is evolving as we speak. Some
researchers still do not accept the grade 7 and do not assign it to meteorites. So if
you see a H4-7 for sale as the worlds first meteorite classified this way just
keep in mind all it really is in fact the first time a specific researcher
decided to classify it this way today. There are probably several other examples
of this grade in the 30,000+ meteorites out there but when it was originally
classified (say thirty years ago) the 7 was not in existence nor was the usage
of - to indicate brecciation.
Now for the pop quiz; based on the information posted on the m-list (and to
see if anybody read this far) is the most likely classification for Amgala
H3.7/5 or H3.7-5? Tell me why you picked one over the other. You must have a
detailed answer-no guesses accepted. No, you will not be graded. But if you get it
correct you will be an official Jr. Meteoriticist B.S. (heavy on the BS :) ).
Anyone getting it wrong will be sent to the corner.
BTW I have not seen the original research and do not know the correct answer.
But have a strong opinion based on several posts to the m-list. We will know
the approved classification when it is published in the MB.

Mike


Mike Jensen IMCA 4264
Bill Jensen IMCA 2359
Jensen Meteorites
16730 E Ada PL
Aurora, CO 80017-3137
303-337-4361
Received on Fri 12 Nov 2004 12:59:13 PM PST