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PETROLOGIC GRADE 5
- To: meteorite-list@meteoritecentral.com
- Subject: PETROLOGIC GRADE 5
- From: Bernd Pauli <bernd.pauli@lehrer1.rz.uni-karlsruhe.de>
- Date: Sat, 14 Mar 1998 16:18:22 +0100
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Wellmann (a) exhibits a fresh brown/black matrix and nice well defined
chondrules in the black to grey range.
Matt (and everyone else), I don't understand. I thought a petrologic
grade of 5 would indicate chondrules that are not well defined or in
other words, not very distinct. There would not be much distinction
between the boundry of the chondrules and the matrix.
Hello Walter, hello List Members,
Both D.W. Sears (The Nature and Origin of Meteorites, p. 69) and J.T.
Wasson (Meteorites, p. 22) present the 'Van Schmus and Wood (1967)'
table describing the criteria for distinguishing different petrologic
types of chondrites. With regard to chondrules, you find:
a) SEARS:
Chondrule texture Petrologic type
None 1
Very sharp 2, 3
Well defined 4
Readily visible 5 <=
Poorly defined 6
b) WASSON:
Overall texture Petrologic type
No chondrules 1
Very sharply defined 2, 3
chondrules
Well-defined chondrules 4
Chondrules readily 5 <=
delineated
Poorly defined chondrules 6
So Wellmann (a) may well exhibit 'nice w e l l d e f i n e d
chondrules'.
Regards, Bernd