Leucophanite, Calcite, Polylithionite - Mount St. Hilaire, Quebec, Canada

Contributed by: Mark Cole
Date: Apr 11th, 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: 1.5 x 1 x 1.75 inches
Weight: 1.1 oz

Description:
Mont St. Hilaire is a suburb of Montreal in Quebec, Canada and is named for the mountain of the same name. There are several working quarries in the area on the slopes of Mont. St. Hilaire (MSH), of which the Poudrette Quarry is perhaps the most famous (actual several quarries merged into one - Demix, Desourdy, and others).

Over 400 mineral species have been identified from the area with over 60 type locality minerals. This alkaline complex is home to many spectacular fluorescent minerals, including sodalite (hackmanite), leucophanite, polylithionite, catapleite, zircon, calcite, and several more. Leucophanite is the most fascinating to me. Only found in a few places around the world (Greenland, Norway, and MSH), the pieces from this area are almost always small crystals/partials. Only Norway offers up massive matrix pieces - so striking under UV.

Presently collecting opportunities are quite limited at the Poudrette Quarry. Pity, because these are some really beautiful fluorescent specimens. The closeup below shows a pinkish/violet, fluorescent leucophanite crystal surrounded by sheets of yellow fluorescing polylithionite, dull red fluorescing feldspar, and bright red calcite. Full size pictures in the gallery below.

Originally posted by Mark Cole on Nature's Rainbows in 2017.