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[Parvin]

What makes calcite fluoresce blue under short wave? What trace element? What impurity?

[Mike Wood]

I have read (maybe an outdated source) that 'Iceland Spar' (presumably from Iceland?), sometimes shows a 'dull, blue luminescence' which was thought to have been caused by defect centres in the crystal lattice.
Calcite normally fluoresces yellow/orange/red and is usually caused by a small amount of Mn2+ substituting; in the range of a few hundred to a few thousand ppm. Apparently some REE such as Dy3+ and Sm3+ substituting in small amounts can produce a very similar colour range.
However, this info is over 25 years old and it is very likely there are more explanations available these days!
Mike

[Pete Modreski]

And, my understanding is that it is high Europium (Eu2+) that causes the blue fluorescence.

Pete

[Mark Ost]

Calcium is not intrinsically fluorescent and requires activators such as Uranium or Europium. I have the typical red fluorescing calcite, but also green, more rare due to uranium content, and some yellow. My Icelandic spar shows no trace of color or afterglow under any frequency of UV.

[Parvin]

Hi Pete,

I have tried to use Eu+2 in order to make calcite fluoresce blue, but it didn't work out. Also, Eu is very expensive, Do you have any idea like what other activators cause calcite emits blue color?
Thanks so much.

Parvin

[Rei]

Parvin: What exactly are you doing with europium? Just dipping the calcite in it? Colors are due to small amounts of impurities in the crystal lattice (or defects in the lattice) - they're not surface treatments.

For what it's worth, I find a lot of massive calcite on my land in Iceland, and I've never found a specimen that fluoresces under UV (I've tried two frequencies). I always do my tests in the laundry room, and bleached white socks kick off a lot more glow than my calcite ;)

Sometimes a specimen just is what it is. There are all sorts of ways you can handle specimens, and sometimes they can make a world of difference. But a lot of things about a piece just can't be changed. If you want to make glowing calcite rather than finding it, you're going to need to grow it from scratch. Or paint it with glow-in-the-dark paint. ;) Hey, if you wanted to shell out the money you could use tritium paint, that'd be pretty awesome - it'd look like something straight out of a comic book ;)

[lluis]

Hi, Parvin

For what I found, blue color seems due to Eu2+ and Eu3+, acting cerium as activator....
So, probably you should use the three elements

Maybe you find this article interesting for your purposes....
https://www.fluomin.org/galeriespectre/spectre.php?lg=fr&name=CALCITE
(link normalized by FMF)

With best wishes

Lluís

[Josele]

[Parvin]

Thanks, I will do.

[Parvin]

Josele,

So, you are saying that even with those three activators, it won't be possible to get the blue color? At what wavelength we should see the blue color?
Thanks.

Parvin

P.S. I am mixing the Eu doped in solution of chloride with ammunium carbonate in order to precipitate calcium carbonate.

[lluis]

Hi, Josele

I am not in fluorescence... Just chemist...

But, even with what you say, seems that in the article the blue calcite has the two states Europium. And the cerium.
Cerium is just the activator: it absorbs UV and transmits energy to Europium...
No color, no fluorescence... Just transmitting energy from UV to Eu... So, no Ce, no fluorescence....

Hi, Parvin: if you use only Eu, without activator, maybe you would not see fluorescence because no energy is transmitted to Eu.
By the way, the precipitation, seems that should be done at 70ºC, and precipitate should be treated thermally (in one I read at 1000ºC in CO2 atmosphere....).
Then, maybe you simply do not fit the required conditions....: thermal treatment and activator...

With best wishes

Lluís

[Parvin]

Hi Lluís,

Could you please tell me what article you are exactly referring?
Thank you.

Parvin

[Josele]

Will see blue color when emission is in 450 - 500 nm range

In the abstract of the cited article about blue luminescence you can read: ... Both centers have spectral-kinetic properties very unusual for mineral luminescence, which in combination with extremely low impurity concentrations prevent their identification with specific impurity related emission. The most likely explanation of these observations may be the presence of radiation-induced luminescence centers.
If Michael Gaft doesn't know it, who knows it?

I'm curious of a more detailed explanation of your system to obtain doped calcite.
Can you describe the procedure? Did you get any results? Can you post some photos here?

[lluis]

Parvin, the article is the one that I placed in my first message...
Long, besides.

Josele: Don is as human as us. He could be right...or he could be wrong.
In complex theory, were many, till last that seems right. Were the predecessors wrong? No, they just didn't have all the info.
When the wave function was generated by Schrödinger, Bohr said that it was the reality, and Einstein said that it was a way to explain reality....
As many heads, as many huts....

Anyway, I am fond to remember that a young lady was the one that showed that skeletal galenas were fake...when they have been sold by many seasoned experts....

So...

For colors..: Pt uses to be slightly yellow and with chloride ions, strong brown. But a cis-platinum is green..... (complex theory....).
Europium could be whatever. But if in calcite, in the right place, it creates the blue fluorescence.... As I said, if not wrong in such article, a blue fluorescent calcite had Eu2+, Eu3+ and cerium (as activator).
More.... Pb is in color...But amazonite is green due to Pb (color centers due to faults in crystal net due to different sizes....)
Then, nothing surprises me..... : things are and explanations, well, our work (the humans work, I mean)

With best wishes

Lluís

[Josele]

I've been checking all calcites in my collection looking for a blue fluorescence, without result. About a third part showed a significant fluorescence. In this benchmarking of some representative specimens, we can see a small part of the diversity of luminescence in calcite, due to different activators, co-activators and combinations, and this gives an idea of the complexity.