[Rockhounds] Question, Cobaltian Calcite

[Axel Emmermann]

> Thank you for the comments and insight, Axel.

Your welcome, Pete! You can always count on me to make an already confusing
situation worse ;-)))
I'd rather call my comments and insights "speculations in the process of
thinking out loud"...

> Since cobalt is "known" to be a "quencher" of fluorescence, I 
> would be very surprised if any cobalt-bearing calcite could 
> also be fluorescent.

Yes. I am too!
Then again, I was always convinced that Iron was a quencher... Turns out it
usually is BUT that it can act as an activator in quite a few pretty
fluorescing specimens. 

> But I can think of more reasons to make this more 
> complicated.? For one, cobalt can be present as either cobalt 
> (II) ions, or cobalt (III) ions, Co+2 or Co+3.? 
>I believe 
> that the former usually colors compounds pale pink, and the 
> later, intense pink, just as Mn+2 is pale pink and Mn+3 is 
> intense red.? Calcite containing Co(II) would properly be 
> called "cobaltoan calcite", whereas that containing Co(III) 
> is what should be called "cobaltian".? It's possible that 
> only Co+2 is a quencher of fluorescence, and that the 
> cobaltian calcite is in fact colored by Co+3, which is not a 
> quencher, and does not prevent Mn also present, from causing 
> fluorescence.

this is my three cents and layman talk... Take it with a  grain of salt...
But here goes:

Hm... Co3+ in calcite? 
It would surely affect the way the CO2 behaves, wouldn't it?
Ca2+ + (CO2)2- would then create e- centers by ligand and become Co3+ +
((CO2)2- + e-)? 
Would that, in its turn, not affect the location of any manganese emission
peak by crystal field effects? 
Some of the oxygen ions in the octahedral configuration (was it?) that
enclose the manganese would be more negative (one "almost" O3- for every
Co3+ that replaces Ca2+). 
Also, would Co2+ and Co3+ when both present in significant amounts engage in
charge-exchange like Fe2+ an Fe3+???
In my vivid imagination it would indeed (I sound like T'ealc in Stargate 1
;-) be possible for the calcite to be darker in daylight color but VERY
unlikely to fluoresce... 

We would have to get back to this once I get the specimen near a
spectrometer. ;-))) 

> [P.S., I seem to have hit some kind of a key while typing 
> this message that has changed the appearance of the font, and 
> I can't figure out how to change it back; I'll see what it 
> looks like when this message posts, and I hope it doesn't 
> come out looking too weird or illegible!]

Nope, looking good, Pete.