[Rockhounds] Terlingua-type calcite

[DonH]

Hi Axel,

That makes sense in as much as I know crystal field theory.  However, 
learning crystal field theory requires a suspension of sanity and 
opening one's mind to the concept that an electron is both a particle 
and a wave, among other things.  It is so arcane that even in advanced 
mineralogy class, we only touched upon the basics.  The rest is very 
elaborate and ponderous mathematics.  But yes, the bonding behavior and 
the electron transitions that produce color are governed by the orbital 
configuration and by the structure into which an atom is bound.  In 
addition, some color effects are anisotropic, which means they are 
dependent upon the orientation of the material relative to the light 
entering it.  Most people know this as "pleochroism" or "dichroism", 
among other terms.

best,
Don