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Re: Coprolites (or "Why X-ray paleo-poop?")



Phillip Bigelow wrote:

> Fossil biogenic apatites that have not been subsequently altered
> (replaced or recrystallized) always had a uniform crystallite diameter
> and have a preferred crystallite orientation.  When the specimen is
> ground-up and placed in a powder mount, these characteristics are
> maintained (the xls self-align slightly due to the handling process).
> The pattern was skewed slightly and sometimes had a moderate degree of
> peak kurtosis.  In contrast, mechanically-powdered
> non-biologically-formed apatites show the typical random cleavage planes
> and shapes of the igneous (and diagenetic) mineral apatites.  These
> feature showed up on the X-ray diffraction pattern in the form of much
> more symmetrical diffraction peaks.

Just out of curiosity, could this difference be enhanced?  I've never seen the 
technique 
and don't know the mechanics, but I was thinking of something in the nature of 
floating 
the sample onto the X-ray target as a packed monolayer on acetone (or some 
other 
reasonably polar solvent).

I'm also wondering if the differences you describe would show in a coprolite 
sample.  
Since the apatite content is pretty low, would there be much tendency for the 
crystals 
to orient with respect to each other?  Or are you talking about a sample after 
some sort 
of fractionation?

  --Toby White