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Calcite green fluorescence activator

Posted by José Zendrera  
avatar Calcite green fluorescence activator
June 04, 2012 01:44AM
Hi all,

Last night I discovered that a large calcite aggregate placed in my garden is so fluorescent. All fluo calcites in my collection turns to pink with UV but this one turns to green. Can somebody tell me how rare is this?

I have understood that the activator of pink fluorescence in calcite is manganese. Have you any idea about wich element could be the activator of green fluorescence in calcite?

Very thanks for your comments.

Parallel grow calcite aggregate with karstic origin on Miocene bioclastic conglomerate.
45 x 35 x 30 cm

Same view under LW UV LED.

Side view.

open | download - C_rom10.JPG (302.8 KB)
open | download - C_rom11.JPG (311.5 KB)
open | download - C_rom12.JPG (336.6 KB)
Re: Calcite green fluorescence activator
June 04, 2012 03:15AM
Considering the origin, I would guess the green is from organic inclusions.

Henry Barwood
Troy University
Troy, Alabama USA
Re: Calcite green fluorescence activator
June 04, 2012 04:21AM
I would also consider the possibility of organic minerals as activators, however, another possibility are uranium oxides, the usual activator in green fluorescing opal and hyalite.
avatar Re: Calcite green fluorescence activator
June 04, 2012 02:28PM
Henry, Errol, very thanks for your help. After reading your post, I found some literature about organic compounds and uranium as fluorescence activators in calcite but I could not find any photo of calcite green fluorescence, I imagine is a unusual phenomenon.

This calcite is from a old Roman quarry exploted many centuries ago to built Baelo Claudia (Tarifa, Cadiz, Spain) not far from my home. I will come back there by night to chech if all calcite in the quarry is fluorescent or not.

Thanks again and greetings.

* please see my thread about fluorescence here (in spanish but with nice pictures):

Re: Calcite green fluorescence activator
June 04, 2012 03:46PM

My guesses were the same; however, much aragonite fluoresces this dull greenish color. Is it possible that it is aragonite intergrown with the calcite??
Re: Calcite green fluorescence activator
June 04, 2012 06:50PM
^Hard to say the aragonite is entangled with the Calcite as they have the same chemical composition.
Re: Calcite green fluorescence activator
June 04, 2012 09:02PM
Look at the cleavage. Calcite has 3, aragonite only 1 (at least only 1 distinct cleavage). The two weak cleavages in aragonite are also at right angles (orthorhombic).

Henry Barwood
Troy University
Troy, Alabama USA
Re: Calcite green fluorescence activator
June 04, 2012 10:05PM
Hi everyone,
I have fluorescent lamp, but I don`t know is it short vave or long vave UW. There is no details on it.I can only say ,that my teeth glow jellow in that light.
Thanks you all.

avatar Re: Calcite green fluorescence activator
June 05, 2012 01:30AM
Thanks for your comments and suggestions.

Even if it were aragonite, green fluorescence would be uncommon. But not, is not aragonite, as the crystals are so large, was easy to check the cleavage as pointed by Henry: always rhombohedrons with 3 cleavage planes.

Perhaps is not rare at all, I found another calcite in my collection with greenish fluorescence. The mystery remains in the activator. I imagine the proportion of activator element is so low that it will not appear in a XRD nor a EDS.

Thanks and greetings.

Candesa Quarry, Verdenueva Height, Camargo, Cantabria, Spain.
10 x 7 x 7 cm
With halogen lamp:


open | download - C_cam0.JPG (176.6 KB)
open | download - C_Cam7.JPG (291.7 KB)
avatar Re: Calcite green fluorescence activator
June 05, 2012 02:01AM
Jose says:

"I imagine the proportion of activator element is so low that it will not appear in a XRD nor a EDS."

Sadly that is too often too true and is just as true for colour in visible light.
Re: Calcite green fluorescence activator
June 05, 2012 12:57PM
Hello Jose,

What makes something glow? Aside from LED lights, the following is from one of my "old" chemistry textbooks, concerning phosphorescence. Generally the metal activators of phosphorescence and fluroescence are similar so maybe this is of interest. It may pose a challenge for us of today to reproduce these experiments, considering obtaining thallium salts etc. grinning smiley

From “Textbook of Inorganic Chemistry”, J.R. Partington, 5th Edit. 1939, pp 847.
Phosphorescence: “The property of shining after exposure to light, especially sunlight”

Phosphorescent calcium sulphide is obtained by heating a mixture of calcium carbonate and powdered sulphur for an hour to dull redness in a closed crucible. The mass is cooled and triturated with an alcoholic solution of various heavy metals to give 1 part of metal to 10,000 parts calcium sulphide. The mass is dried in the air and heated to dull redness for two hours and then slowly cooled.

Various phosphorescent masses are prepared by heating the mixtures A below, powdering the product, moistening with solution B, and re-heating. (All weights are in grams and volumes in cubic cm).

A: 20g calcium oxide, 6g sulphur, 2g starch, 0.5g sodium sulphate, 0.5g potassium sulphate.
B: 2cc of 0.5% bismuth nitrate solution plus 0.5 cc of aqueous thallium sulphate.
A: 20g calcium oxide, 20g barium hydroxide, 6g sulphur, 1g potassium sulphate, 1g sodium sulphate, 2g lithium carbonate, 2g starch.
B: 2cc of 0.5% alcoholic bismuth nitrate plus 2 cc 0f 1% rubidium nitrate solution.
A: 40g strontium carbonate, 6g sulphur, 1g lithium carbonate, 1g arsenic trisulphide.
B: 2cc of 0.5% thallium nitrate solution.
A: 40g barium carbonate, 6g sulphur, 1g lithium carbonate, 0.47g rubidium carbonate
A: 25g barium carbonate, 15g strontium hydroxide, 10g sulphur, 3g starch, 1g lithium sulphate, 1g magnesium oxide.
B: 2cc of 0.5% thallium sulphate plus 3cc 0f 0.4% copper sulphate solution.
avatar Re: Calcite green fluorescence activator
June 05, 2012 03:03PM
Manuel Robbins, in his book "Fluorescence", Geoscience Press, 1993, page 76, indicates that Terlingua calcites can fluoresce a pale green. He does not indicate what the activator may be; however on a later page he says that organic activators cannot be ruled out.
avatar Re: Calcite green fluorescence activator
June 06, 2012 12:56AM
Thanks David, the list seems a good recipe! Thanks Don for the reference.
Below I post another calcite from same Roman quarry, also very fluorescent.
I'm beginning to think that this material could not be rare, the quarry is full! However, I have some other stalactite samples from different places and are not fluorescent.
The quarry is the Gibralter Strait Natural Park, not far from de beach but 200 m.a.s.l. There is no road, is a 30 minutes walk from home. Next new moon I will go to check if the quarry is all fluorescent...
18 x 14 x 14 cm
With halogen lamp:


open | download - C_15.JPG (325 KB)
open | download - C_16.JPG (323.6 KB)
avatar Re: Calcite green fluorescence activator
July 09, 2012 07:50PM
More surprises with this calcite. Yesterday I walk up to the Roman quarry where this material come from and I picked up another piece of karstic calcite. When, at night, I checked the fluorescence with a UV LED lamp, I can't belive that I see: this piece has a pink fluorescence, not green as the other pieces from same area.
There is many karstic calcite veins in this area, I imagine that different fluorescence colors must be due to different activators. One of these nights I will check the fluorescence "in situ" and I will post the results. Meanwhile, comments will be very welcome.

The quarry was used by Romans to construct Baelo-Claudia, in Tarifa, Cadiz, Spain. They prepare rough column sections at place, then they roll them to the beach (pine forest are new, this slope was a dunes erg), and transport the blocks by sea to Baelo-Claudia, 3 miles away.
The karstic calcite is in some veins as can see in the center of the wall.

Karstic calcite under halogen lamp.

Karstic calcite under UV LED lamp.

open | download - Roman quarry.JPG (251.5 KB)
open | download - calcite11.jpg (261.9 KB)
open | download - calcite12.jpg (222 KB)
avatar Re: Calcite green fluorescence activator
July 10, 2012 11:45PM
I hope not to bore you with this topic but I want to show you this. In this layered karstic calcite, some layers are fluorescent and some others are not, as can see in last pictures. Today I discovered a big piece with some layers turning to pink and some others to green under LW UV. Different layers have different activators due to different crystalizing conditions and / or different composition of water salts?

With UV LED 390 nm:

With halogen lamp:

open | download - C_karst21.jpg (250.8 KB)
open | download - C_karst22.jpg (197.4 KB)
avatar Re: Calcite green fluorescence activator
July 11, 2012 12:23AM
Jose, if you are serious about Fluorescents you should check out The FMS is currently developing a huge catalogue of Fluorescent Calcites and yours would be a good addition if not already there. They may know what your activators are. Your suggestion that traces in the depositing fluids produce the colours must be right.

Anyone seriously interested in Fluorescents should join up.
Re: Calcite green fluorescence activator
July 11, 2012 12:07PM
Jose, your mention that this is karst-related provides some clues -- so we are apparently looking at near-surface, low-temperature calcites. Rainwater percolating through soil horizons often picks up humic and fulvic acids that form by decomposition of organic materials in the soil above cave systems. As the rainwater percolates downward through the soil horizon into the rock below, eventually to become part of the groundwater system, any calcite deposited along the way in fractures, or as stalactites, stalagmites, flowstone, etc. in the caves is apt to fluoresce because of organic activators. The organic molecules are far too large to fit into the calcite crystallographic sites, so they are present as molecular inclusions. The resultant fluorescence can cover a broad range of colors depending on which humic and fulvic acids are present and can be green, white, pink, pale blue, etc.

Here are a few guidelines:
1. Cave calcites with organic activators almost always fluoresce in some pastel (unsaturated) color: white, pink, pale green, bluish white, etc. Rich, vibrant colors would make me think of another cause. From your photographs the fluorescence seems to be pastel, consistent with organic activators.
2. Such calcite usually fluoresces more strongly LW than SW. Often the fluorescence can be activated by visible light as well, as cavers often note when sweeping their cap lamps across a cave passage and seeing a phosphorescent trail.
3. Phosphorescence is often noted in such calcites. Often the phosphorescence has a slightly "cooler" color after SW excitation than after LW. I've noted many examples where the phosphorescence after SW excitation is bluish white, but after LW excitation it is greenish white.
4. Uranium in the form of uranyl ion is another quite common cause of green fluorescence in many species (calcite, aragonite, opal, adamite...), again as molecular inclusions. However, the color of fluorescence is saturated, a vibrant yellowish green, quite unlike the pale greens caused by organic activators, and usually the fluorescence is much brighter SW than LW. Phosphorescence is usually absent.
5. Bear in mind that uranyl-activated calcite can also be found in caves (as in some of the Grand Canyon, USA occurrences), and both organic and uranyl activators of fluorescence, as well as others, can be present in the same specimen.
avatar Re: Calcite green fluorescence activator
July 12, 2012 02:28AM
Ron, following your advice, I signed up in FMS. Is a very interesting site and now I need some time to read and digest the large amount of information it contains, these days I'm busy and I still could not do it. Very thanks for your help.

Earl, thanks very much, your explanation is very helpful to understand what my eyes are seeing. I had noticed a slight phosphorescence but I thought it was psychological, from now will observe this phenomenon with more attention.
Regarding the origin of activators, the more I learn, the less I understand. At first I thought maybe you could correlate the fluorescent layer in the different veins of the quarry and see if they are contemporary, as we do in a sedimentary geological formation. But I'm not so sure I see that the cementation of the sandstone limestone containing calcite is also fluorescent at some points and they are scattered without any apparent order.

The geological history of these sandstones is short and quite thrilling. Are very young, dated as Early Pleistocene, deposited in proximal marine environment and are currently about 200 meters above sea level. Tectonic movements in the Strait of Gibraltar led to his fast climb, during which eroded most of the deposit, leaving only isolated outcrops here and there in discordant contact on older materials.
I think I will need a lot of dedication to study the fluorescence of these materials and to draw conclusions useful for the understanding of these sandstones.
I will come back again when the checks and photos of the quarry are done.

Wall cut from the Roman quarry. In the cave lies the fluorescent calcite:

Wall section of fluorescent calcite:

open | download - romanquarry7.jpg (374.3 KB)
open | download - romanquarry9.jpg (489.7 KB)
avatar Re: Calcite green fluorescence activator
July 12, 2012 01:49PM
Howdy All,

Many micro and macro sea organisms fluoresce, in various shades of green. Based on the location and age of the sandstone, plus the history given; I would suggest the fluorescence is quite likely a result of the CaCO3 being of marine origin (ie: broken down shells and exoskeletons etc.).

Given the climate will have changed little from the time of the deposition of the sandstone beds, to today, it would be fair to say that any calcite or calcrete deposits close to the surface may well have gone through numerous stages of saturation followed by drying (possibly even crystalisation).

* Calcrete (also known as caliche or kunkar) - This rock-like material forms as a soil horizon, by seasonal winter-time wetting (which dissolves the CaCO3) and summer-time drying (which precipitates the CaCO3 as a solid again). The original source of CaCO3 may have been either; part of the sandstone composition or shell grit in wind blown sand from the coast.
You will find this action is actually still happening constantly in this region today.
Extreme periods of wet can move the CaCO3 quite deep into ground if given enough time and fluid.

So being so close to the surface, even if the base deposit of calcite was hydrothermal, both it and any further additions to the deposit would almost certainly have been affected by the weather cycles and the deposition of marine based CaCO3.

The fact the sandstone has undergone periods of uplift and folding etc, I would not be at all surprised if the deposit is a mix of hydrothermal and weather based deposition. Thus; the pinkish fluorescence in some pieces, and green fluorescence in others. It is just a theory, but it may explain the results given.
I would certainly recommend the sandstone be checked under a microscope for traces of fossilised marine organisms and be tested to determine its CaCO3 content.

Just as a quick note: Calcite can also crystalise quite quickly if given the right conditions.

Hope this helps some!

Cheers Mark.

We will never have all the answers, only more questions!

Edited 1 time(s). Last edit at 07/12/2012 01:58PM by Mark Willoughby.
avatar Re: Calcite green fluorescence activator
July 12, 2012 03:26PM
Just to confirm that Mark is right assuming this sandstone has marine fossils:

This is a bioclastic sandstone containing many fossils, specially bivalve molluscs. Is locally conglomeratic (in photo), with some boulders up to 10 cm and fossils up to 5 cm:

Here karstic calcite "in situ" near to a conglomeratic zone:

I hope to post soon some pictures of the quarry by night with UV lighting.

open | download - romanquarry3.JPG (505.4 KB)
open | download - romanquarry4.JPG (483.2 KB)

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