Polylithionite, Leucophanite, Albite, Serandite, etc. - Mont Saint-Hilaire, Quebec, Canada

Contributed by: FMS Admin
minID: TTT-X28
Date: May 18th, 2026
Locality: Poudrette quarry (De-Mix quarry; Demix quarry; Uni-Mix quarry; Carrière Mont Saint-Hilaire; MSH), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada (See on Mindat)
Size: 6.3 x 5.2 x 7.7 cm

Description:
Shown here is a gorgeous combination of polylithionite, leucophanite, serandite and others, on albite crystals. As usual, the polylithionite fluoresces yellow under shortwave; the leucophanite crystals (largest leucophanite crystal: 7 mm) also react to SW but are at their best under MW. Under longwave, only the leucophanite dimly fluoresces a weak purplish pink. The purple seen in the LW picture is indeed actual fluorescence and not mere lamp reflections - tested with a piece of polycarbonate between the UV lamp and the specimen. The albite fluoresces the typical dull red SW response of feldspar; and under MW, small dots of red fluorescing calcite show up (also reactive to SW but much weaker).

Overall, this specimen is at its best under SW and MW combined; it is also aesthetic in visible light. Shown in the first picture is the response under midwave and shortwave combined.

Originally posted by Frédéric Messier Leroux on Nature's Rainbows in 2021.