Fluorite {was: Re: [Rockhounds] quartz sphere question}

[Axel Emmermann]

 Hi Kreigh and Carolyn,

> 
> "Although  Engelhardt  made  the  statement  that  organic compounds
> must be regarded as being responsible for the  fluorescence of
> fluorite,7 

[Axel] 
In most cases you would be able to see the droplets of HC or petroleum under
a stereo-microscope or even with a strong magnifying glass. In the
Rosiclaire and Cave-in -Rock specimens I saw, the unaided eye is all you
need ;-)))
In yellow fluorite from Moscona, Spain, the organic matter is dispersed in
the form of a very fine dust. Every other crystal or so has a dark inclusion
of a tar-like substance but without that it would be real hard to tell if
the mineral fluoresces because of an activator or if it's contaminated with
hydrocarbons.

> it  would now appear, according to the recent investigation
> of ranaka,8  that  in  many instances the  rare elements samarium,
> yttrium,  thallium,  and others, are the chief activating agents.

[Axel] 
Yttrium is not a rare earth element in strictu sensu... It shares lots of
their properties and is often regarded upon as one.
If it replace a substantial part of the calcium in fluorite you get
yttrium-fluorite which fluoresces yellow.
Europium would cause a blue fluorescence and rumour has it that samarium
could be the cause of a red fluorescence. 
Manganese and Erbium cause green fluorescence (if I remember correctly).

> Engelhardt's conclusion is probably  true for  certain specimens of
> fluorite, as for example the one just described, but  the rare element
> theory  seems to  ofier  a  better  explanation  for  most fluorescent
> fluorites.  

[Axel] 
There is also the possibility of e-centers in zones of disturbed crystal
growth. This has been investigated by Prof. Renaud Vochten (Vochtenite).  

I'm sure that the last word about fluorescence hasn't been spoken yet.

Cheers
Axel