FMF - Friends of Minerals Forum, discussion and message board

[waterdog]

I have some specimens of calcite flowstone from an old mine dump. The flowstone fluoresces a strong yellow to golden yellow where it was exposed on the surface of the dump but fluoresces a weak white/gray on what were unexposed surfaces. The fluorescence is under both longwave and shotwave UV. The unexposed surfaces usually, but not always, phosphoresce as well whereas the exposed surfaces rarely phosphoresce. The mine dump was created about a hundred years ago so the exposure time of the flowstone has been no more than that. The miners had used a small solution passage to work their way underground in order to intersect a limestone/dike contact. Remnants of the flowstone still in place underground fluoresce gray/white and only weakly. I have placed some of the specimens in the yard where they have been exposed to sunlight for several months with no discernible change in fluorescence/phosphorescence.

The attached photo shows yellow fluorescence where the specimen was exposed on the surface of the dump while the blue-gray areas were buried in the pile. Note that the blue tint is an artifact of the camera sensor and is not visible to the naked eye. The orange areas are calcite veins that strongly fluoresce orange under shortwave UV and yellow under longwave UV light. Surface exposure shows no effects on the fluorescence of the vein calcite.

My current hypothysis is that sunlight is affecting the fluorescent properties of the calcite. Has anyone else encountered this phenomenon?

[Josele]

Yes, I noted the same phenomenon in an old Roman quarry on karstic calcite. You can see a report here and a complete report of the quarry here (Spanish)

We can comment more details next days.

Happy new year!!!!

Can see an HR version of third photo here

[waterdog]

Thanks for the report. The Roman quarry site is fascinating. Organic activators would make sense for the yellow/white fluorescence in my flowstone samples.

I had the opportunity to shoot a few of the specimens with a x-ray fluorescence analyzer. The orange fluorescing vein calcite showed an average manganese content of 1800ppm while the flowstone showed only 70ppm. Lead concentrations were simularly split with 2600ppm lead in the orange vein calcite and 100ppm lead in the flowstone and zinc at 1200ppm vs 240ppm.

[Parvin]

Hi, I wonder if anybody does the synthesis of fluorescent calcite with Manganese. I am following Fonda's studies, but didn't work out. I wonder what was his trick?