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

From: Jeff Grossman <jgrossman_at_meteoritecentral.com>
Date: Fri Nov 12 17:53:54 2004
Message-ID: <5.1.0.14.2.20041112174311.02aa9ff8_at_gsvaresm02.er.usgs.gov>

Mike is not quite right. The hyphen means it's a breccia spanning at least
the range of specified types. So H3-6 means it's a breccia containing H3,
H6, and possibly (but not necessarily) everything in between. The slash
means the person could not tell, or, sometimes, that the meteorite is
transitional. If somebody classified something as H3/6 it means he/she
didn't know what he/she was doing. H4/5 means that the classifier couldn't
decide between types 4 and 5. L/LL4 often means that fayalite content was
transitional between L and LL. And yes... there are some old
classifications that used - and / in the opposite sense, before the NomCom
wised up to the problem.

jeff

At 12:59 PM 11/12/2004, Mikestockj_at_aol.com wrote:
>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
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Dr. Jeffrey N. Grossman
Chair, Meteorite Nomenclature Committee (Meteoritical Society)
US Geological Survey
954 National Center
Reston, VA 20192, USA
Phone: (703) 648-6184 fax: (703) 648-6383
Received on Fri 12 Nov 2004 05:53:43 PM PST