• Frédéric Messier Leroux

"Terlingua-type" calcite with unusual yellow midwave UV response

A few months ago, I purchased this nice and quite big cleavage rhomb of "terlingua-type" calcite, from the Challenger Cave, Nuevo Leon, Mexico. Took me a while before shooting and posting it, since I waited until receiving my new spot cleaning gun to remove some unsightly bruising on some of its edges (these small cleaning guns, with the nozzle adjusted to generate a thin "needle jet" are powerful enough to remove bruises and chisel marks - any perfectionnist collector should get one). The intensity of the fluorescence is reduced in bruised areas, and bruised specimens don't look good in daylight in my opinion. Some imperfections are still remaining but the specimen is in much better shape now than it was when I received it.

While not being as gemmy as I would like it to be, it's still a really lovely piece, both under various UV wavelengths and in visible light; and its yellow response under midwave UV is really nice. As usual, it reacts not only to UV light but also to blue light and green light; I didn't include pictures of the green and blue light responses, but will eventually , as soon as I have the required filters. But, instead, I shot it not only under 365 nm longwave UV but also under 395 nm LW UV; the response under this wavelength is yellowish cream-white. Under 450 nm blue light it is bright yellow. The response to green light is orange-red; it is easier to observe with a green laser, and doesn't require filters. But since this specimen lacks transluscency, it was not worth taking pictures of the green laser fluorescence, which is much better seen in the gemmy specimen in my next post.

Shown respectively: SW UV fluorescence, SW phosphorescence/"afterglow", MW UV fluorescence, MW phosph., LW UV (365 nm) fluorescence, LW UV phosph. (a short-lived blue flash, unlike the long-lasting SW & MW afterglow), 395 nm LW UV fluorescence*, and lastly, visible light.

*The 395 nm picture was edited in photoshop to remove the purple/blue visible light bleed from the 395 nm light source.

Size: 8,4 cm X 6,2 cm X 3,8 cm

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