Famous also for its tenebrescence or reversible photochromism: it darkens to pink or red after exposure to UV light, and bleach back to its normal color (usually white or light pink, but also blue) with a strong white light.
Best (only?) samples are from the Ilímaussaq complex in Greenland.
SC1165 – Tugtupite from the Ilímaussaq complex, Greenland
Fluorescent tugtupite in my collection:
SC1165 – Tugtupite from the Ilímaussaq complex, Greenland
Tenebrescent tugtupite: normally pink, it changes color to a darker red upon exposure to UV light....