[meteorite-list] Classification of Chondrites Without a Number

From: Jeff Grossman <jgrossman_at_meteoritecentral.com>
Date: Tue, 17 Aug 2010 14:27:48 -0400
Message-ID: <4C6AD4A4.5060808_at_usgs.gov>

Reasons for not giving a petrologic type these days might include:

1) The classification was not done using a thin section. Pet type is
hard to determine in reflected light or based on hand samples.
2) The meteorite is so badly altered that you can't tell the pet type.
3) The meteorite is an impact melt rock, where pet type is not defined,
but you can still tell the parent group based on mineralogy.
4) The meteorite is so small that you can't see enough area to determine
pet type.

In the past, especially at the dawn of the modern classification system
in the 1960s, the analyst may just not have determined pet type prior to
publication.

Jeff

On 8/17/2010 1:41 PM, Thunder Stone wrote:
>
> Hi List:
>
> Here is something I've wondered for a while and I hope someone can answer it for me.
>
> Why are some Chondrites only classified as a 'L' or 'H' or in some cases 'EH' and 'E'
>
> Is it just the way classifications were done in the past and is it possible to probe the samples and give them the appropiate number? Or do they fall out of the 3-6 range? I do see some in the 2000's classified in this manner. Perhaps the institution the classifications were done?
>
> Much Thanks,
>
> Greg S.
>
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Received on Tue 17 Aug 2010 02:27:48 PM PDT