[meteorite-list] Doing your own preliminary MOSS classification

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Aug 31 16:22:55 2006
Message-ID: <DIIE.0000007100000C5D_at_paulinet.de>

Jeff Grossman kindly wrote to Mike Farmer:

"Petrologically, Moss is a CO3. It contains chondrules, CAIs, AOIs, and
metal/sulfide grains in the appropriate size range ... The distribution
of chondrule types is typical for a CO3".

Hi, Happy Moss Owners and Listees!

How about doing your own p r e l i m i n a r y MOSS classification? Jeff Grossman's
first comments contain a lot of information that you can probe into with the help of your
eyes, your microscope and a guide like "HUTCHISON R. (2004) Meteorites: A Petrologic,
Chemical, and Isotopic Synthesis (Cambridge Planetary Science Series, pp. 107-111).

1. It contains chondrules, CAIs, ... in the appropriate size range:

- chondrules and CAIs should be abundant and small (0.15-0.3mm)
  Exception: Adam's new NWA 4439 CO3.3 with its highly variable
  chondrule size

- there should be about 3x as many chondrules as CAIs. Count yours!

2. The distribution of chondrule types is typical for a CO3:

- there should be abraded or fragmented chondrules. Can you find any?

- the majority of chondrules are PO (porphyritic olivine). How many can you see?

- some PO chondrules contain metal that is partially replaced by magnetite
  Can you regognize any black areas with a metallic luster within your POs?

- metal: 1-5 vol%, so, ... guestimate how much metal there is in your piece!

  The fact that Moss seems to be extremely rich in metal prompted Rob Matson in a
  private mail to cautiously assume it might be a CH chondrite (ca. 20 vol% metal!)
  What do you think? Could it be a CH or something ungrouped or an anomalous CO3?

3. According to Hutchison, "isolated single crystals and fragments of olivine are abundant":

- That's a bit difficult without a thin section. My DaG 190 CO3 thin section does show
  several of these isolated single crystals floating amid the other matrix components

4. Many chondrules should have rims of fine-grained opaque material. That's an easy
   task. My DaG 190 slice shows plenty of these dark rims as does my NWA 4441
  (the latter from Greg). Does your Moss slice show them?

Examine, enjoy, and have lots of fun with your
personal preliminary classification before
the official results are published ;-)

Bernd
Received on Thu 31 Aug 2006 04:21:15 PM PDT