[meteorite-list] Re: Petrologic types and point values

From: E.L. Jones <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 10:23:48 2004
Message-ID: <3E70D977.5070904_at_epix.net>

Hello Gents, List

To my best recollection, the decimal value is not a scale from 3 to 4,
such that 3.5 is "half way" would be between the two grades. It is an
index for another characteristic peculiar to feldspathic minerals , I
believe.

The value after the decimal (e.g. 3."X", 3.5, 3.7 etc.) is a index of
the degree to which some feldspar content fluoresces, indicating
another, specific type of metamorphic process beyond the equilibration(
comingling/co-melting) of all types of chondrites as they move from
3-4-5-6 etc. I infer that the process is lost after stage 3 and may be
insignificant(???)

Perhaps someone else would offer the specifics as to who designed the
index and what its significance is. We have discussed this before
 perhaps it is in the archives.

Regards,
Elton

Lars Pedersen wrote:

><snip>?
>But what is the "tecknical" background for 3.2 - 3.8 ?
>I would like to dig a litle bit deeper.
>
>Thanks
>Lars
>
>
>
>>Hei Lars,
>>Even finer grading, lowest value of 3.x means the chondrules
>>are the most distinct, higher values that they become
>>more 'blured'. But even 3.8 are quite distinct since
>>it's 3, not 4,5,6 in the first place.
>>
>>
>>
>>
Received on Thu 13 Mar 2003 02:18:15 PM PST