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This is calcite from the Challenger Cave System near Monterrey Municipality, Mexico. It is “Terlingua-type” calcite. Note “Terlingua-type” calcite, named after the calcite found in the mercury mines of Terlingua, Texas, USA. It has several different responses to different UV wavelengths (see the two graphics below and the video). It is best know for the pink response at 365nm. This color can range from an orangish pink, bubble gum pink, to a lilac (see photograph to right).
Source of Fluorescence
The fluorescence is generally attributed to trace amounts of manganese (Mn²⁺), enhanced by lead (Pb²⁺) and other rare earth elements. Analytical work has also shown that pink Terlingua-type calcite may be enriched in rare-earth elements relative to adjacent white or colorless areas, supporting the interpretation that rare earths may contribute to radiation-damage-related luminescence centers. (Gaft, Reisfeld, and Panczer 2008). I have not found any information regarding the yellow at 340nm.
Geology - I have not been able to find much on the geology. Some writeups indicate the calcite is from speleothems, but I find this very unlikely as speleothems are deposited in layers and I've never seen them produce rhombohedral cleavage...at least not at the size I've seen from the Challenger Cave locality.
This video shows the various response to 365, 340, 312, and 255 nm UV. Note the ones in the lite pink to lilac at 365nm do not show the yellow at 340nm. Only the ones that are orangish pink show the yellow at 340 nm.
The following two graphics show the different responses at different wavelengths. They were created by Nicholas Viltrakis who was kind enough to allow me to share them. You can find him at Facebook, his website, and Flicker.
This emission spectra were generated by Mike Crawford. He was kind enough to allow me to post them here.
This graphic includes the 340nm response. The original post can be found at: https://www.facebook.com/share/p/1C5czH1xXZ/
The following images are some of the mine and miner taken by Antonio Mancini, who was kind enough to allow me to share them. Note - I used AI to clean them up so they will show as AI generated but they are not.
Note: I have purchased several specimens from him and have always been very pleased.
Cliffs of the area.
Entrance.
The man that does the mining.
This specimen was my 2026 Valentine's Day present. Monterrey Municipality, Nuevo León, Mexico
1,100 grams (2.4 lbs)
89 x 66 x 53 mm (3.5 x 2.6 x 2.1 in)
Purchased January 2026 from Antonio Mancini $90
Here is another specimen from Challenger Cave. Note this one is not nearly clear as the one above.
425 grams (15 oz)
66 x 53 x 28 mm (2.6 x 2.1 x 1.1 in)
Purchased December 2025 from John Rofrano II $25.
UV 365 nm
White light
References:
Gaft, Michael, Renata Reisfeld, and Gérard Panczer. 2008. “The Nature of Unusual Luminescence in Natural Calcite, CaCO3.” American Mineralogist 93 (1): 158–167.
https://www.osti.gov/servlets/purl/951771 and https://doi.org/10.2138/am.2008.2576
Further reading:
Mason, R. A., and A. N. Mariano. 1990. “Cathodoluminescence Activation in Manganese‑Bearing and Rare‑Earth‑Bearing Synthetic Calcites.” Chemical Geology. https://www.sciencedirect.com/science/article/abs/pii/000925419090113L
Habermann, Detlev, et al. 1998. “Low Limit of Mn2+‑Activated Cathodoluminescence of Calcite.” Sedimentary Geology 116: 13–24. https://files.secure.website/wscfus/7885803/32229972/mn2-fluorescence-low-limit-in-calcite-haberman.pdf
Walker, Gordon. 1963. “The Sensitized Luminescence of Manganese‑Activated Calcite.” U.S. Geological Survey. https://www.usgs.gov/publications/sensitized-luminescence-manganese-activated-calcite
Mindat.org. 2026. Challenger Cave System, Monterrey Municipality, Nuevo León, Mexico. https://www.mindat.org/loc-435066.html
Nature’s Rainbows. 2016. Calcite Cleavage Rhomb, Challenger Cave, Nuevo León, Mexico. https://www.naturesrainbows.com/post/2016/12/14/calcite-cleavage-rhomb-challenger-cave-nuevo-leon-mexico
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