FMF - Friends of Minerals Forum, discussion and message board

[Josele]

Some days ago I discovered that a karstic calcite from an old Roman quarry that was used to built Baelo - Claudia (ancient Roman city in the coast of Tarifa, Cádiz, Andalousia, Spain) is highly fluorescent. The thing is that fluorescence is not pink as use to be in calcites but green, a bright green.
I have two questions, perhaps you can help me:
- How rare is green fluorescence in calcite? For me is something new, I have not seen this before.
- Which element can be the activator for this green fluorescence?
Comments will be very wellcome, thanks in advance.

[GneissWare]

I think the companion thread on Mindat covers the issues:

https://www.mindat.org/mesg-11-262539.html

Uranyl or organic traces are most likely.

to quote from the Fluorescent Mineral Society website:

A common fluorescent is calcite. It comes in just about all fluorescent colors due to different activators. Red and pink fluorescent calcites are often activated by a team of lead and manganese. Calcite may fluoresce green due to uranyl ion traces. Calcite from the mercury mines at Terlingua, Texas, and just across the border into Muzquiz, Coahuila, Mexico, is a favorite. It fluoresces pink under longwave UV and bright blue under shortwave UV, with a uniquely bright blue phosphorescence after the UV lamp is removed.

[Josele]

[GneissWare]

Given:
Calcite is not inherently fluorescent in pure form.
Its fluorescence is a function of trace contaminants.
Green fluorescence is due to organic compounds or uranyl ions.
Reddish fluorescence is due to lead and manganese.

Then:
As Mn and Pb are more abundant than U in most environments, I would expect green fluorescence to be less common than the reddish form.
Not knowing what kinds of organic compounds contribute to the greenish fluorescence makes a statement about them harder to speculate about. But, organic compounds are probably more prevalent in some environments, like cave systems. So, it will be largely a function of the depositional environment, I would guess.

I don't know of any studies that have quantified how frequently green fluorescence is encountered. Anecdotally, I have seen it several times.

[Josele]

Gneissware, thank you very much, in few words you accurately summarized the matter.
Just a data: I have calcites from about 30 different places and 7 localities shows fluorescence, mostly pink, some turns to yellow, and only one green. That gives more than 23% rate of fluo calcites.
To me, most fascinating thing is that a so small quantity of an element, not detectable with standard analysis, can provoke so showy effect.
Greetings.

Can see more pics here:
https://www.foro-minerales.com/forum/viewtopic.php?t=7665

[Josele]

Some days ago I walked up to the quarry where these calcites come from. I picked up some samples and at home I was very surprised when check the fluorescence because the color: that one is pink.
After wait for a no moon night, yesterday at sunset I walk up again with camera, tripod and some LW UV LED flashlights. Is a very amazing quarry...
You can see a complete report here:
https://www.foro-minerales.com/forum/viewtopic.php?t=7867

[Josele]

This is another outcrop of same Roman quarry. Here we find some karstic calcite covered walls and also some sections showing inner aggregate structures and geodes.
Thanks for your comments, suggestions and information about fluorescence activators, any help to understand little bit more this phenomenon will be very appreciated.

Please, see a report of this outcrop here:
https://www.foro-minerales.com/forum/viewtopic.php?p=79916#79916

or, see a complete report of the quarry here:
https://www.foro-minerales.com/forum/viewtopic.php?t=7867