AW: WG: [meteorite-list] Classification question

[Jeff Grossman]

Not gonna happen.  The types-1 and -2 designations are archaic, even for 
carbonaceous chondrites.  The problem is that some type 3's are aqueously 
altered and some type 2's are thermally metamorphosed.  This is what 
happens when you use one digit to signify two variables.  Since the type 
3.0-6 scale is well defined and the numbers mean something in terms of a 
metamorphic sequence and the type-2 category is just descriptive and 
nonquantitative, it would be a step in the wrong direction to start 
dropping 3.x in favor of 2.

jeff

> > BTW: A petrologic type 2 has never been assigned to any ordinary 
> chondrite. Only to carbonaceous chondrites.
> >
> > Jörn
>
>Hi Jörn,
>
>It was proposed in a paper I read a while back that Semarkona may be
>consistent with a petrographic type 2 classification due to aqueous
>alteration. I guess it's possible.
>
>David
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Dr. Jeffrey N. Grossman       phone: (703) 648-6184
US Geological Survey          fax:   (703) 648-6383
954 National Center
Reston, VA 20192, USA