[Rockhounds] Terlingua-type calcite

[Axel Emmermann]

Hi Don,

I hadn't seen Doug Leeper's response to this issue because it was
automatically moved to the waste-bin.
"Issue" being the key word. All "Rockhounds Digest... Vol..., Issue..." go
directly into the waste bin. I have too little time to go figure out what is
inside messages from people that deliberately obscure the content by
changing a perfectly clear title to something so unimaginative.

I'm sure most of us appreciate how the title of the message changed back  to
"Terlingua-type calcite".  

This being said, you wrote:

>   For example, divalent europium can substitute nicely for 
> calcium in many structures (depending on how many oxygen 
> surround the calcite in the coordination polyhedron), due to 
> its size and charge.  Europium is known to produce a blue 
> fluorescence, though I imagine this is not an iron-clad rule 
> and may depend upon what mineral it is substituted into and 
> also what co-activators exist as well, and also structural 
> defects introduced into the mineral.  On the other hand, some 
> activators are not well documented at all, though there may 
> be educated speculation for some of them.

I'd have to look up the exact page (it's somewhere around p. 200) but I
think that my Marfunin says somewhere that DIVALENT REE don't feel the
crystal field effect much whereas higher valences of REE do. That has to do
with it being not the outer electrons but the "underlying" shell" doing the
transition number on us while shielded by . So the spectrum of Eu2+ in
feldspars, quartz and other minerals should be quite similar (not congruent
but similar) so basically blue. If this is true (if it isn't I'm still
blaming my memory losses on the anesthetics ;-))) then large differences
between spectra of Eu2+ activated minerals would rather be caused by
absorption, other activators, energy exchange between Eu2+ and other REE or
similar elements like yttrium or scandium, inclusion of organic matter and
other minerals.
The very strong electro negativity of Fluor may do "something" to the
spectrum of fluorite or not, but caged in in oxygen-polyhedra there should
be little or no shifts of the peaks that are species-dependent.
Or I'm wrong and it are the trivalent REE that don't react much to crystal
field effects and non of the above is true... Anyway, I'm glad I could clear
that up (very LOL). There, now I've said it. ;-)
I 'm trying to get myself to re-read the entire "Spectroscopy, Luminescence
and Radiation Centers in Minerals" by Arnold Marfunin. I didn't quite get
the full concept the first time around ;-)))
So I thought that my vague ramblings might better be interpreted and revised
by some bright new professional ;-)))

Any sense to be found in this???

Axel