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Darwin-L Message Log 1:186 (September 1993)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

Note: Additional publications on evolution and the historical sciences by the Darwin-L list owner are available on SSRN.


<1:186>From ahouse@hydra.rose.brandeis.edu  Tue Sep 21 12:55:46 1993

Date: Tue, 21 Sep 1993 14:02:24 -0500
To: darwin-l@ukanaix.cc.ukans.edu
From: ahouse@hydra.rose.brandeis.edu (Jeremy John Ahouse)
Subject: Re: Classification in mineralogy

>   Minerals are grouped together in two ways. The true
>classification system is a tree, and is based on the chemistry
>of the mineral. There are sulfides, sulfates, oxides and
>silicates. The silicates are subdivided according to the SI:O
>ratio. Further subdivisions occur on the grounds of structure,
>and the finest distinctions are then made by chemical for-
>mulae, with "subspecies" being solution series between
>interchangeable atoms (example: % Fe vs Mg in a certain
>crystal site).

    It isn't clear to me why this would necessarily generate a strictly
dichotomous tree.  If you had something that was 1/2 sulfide and 1/2 oxide
where would it go?

    Thanks,

    - Jeremy

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