Fluorescent Calcite from Saint-Eustache, Quebec, Canada
Contributed by: FMS Admin
minID: 3TW-0CJ
Date: May 17th, 2026
Locality: Saint-Eustache Quarry (Carrière et pavage Saint-Eustache; Mathers Quarry), Saint-Eustache, Deux-Montagnes RCM, Laurentides, Québec, Canada (See on Mindat)
Size: 3.8 x 3.1 x 6.5 cm
Description:
Last year, while sorting out specimens in my storage, I decided to get rid of all specimens that were not aesthetic or rare enough to be worth keeping in my white light displays. After having put them in a separate box to later give them away, I thought it was a good idea to inspect them under UV just in case some of them were good under UV despite not being good enough in daylight to be worthy of my personal collection.
Then I realized that this little specimen, which is clearly not a keeper compared to average specimens from this locality (the Mathers Quarry in Saint-Eustache, now unfortunately off-limits to collectors), fluoresces brightly enough to be put in my longwave display. The fact that the Mathers Quarry is not generally known as a fluorescent mineral locale makes it an interesting piece in my opinion. I later inspected specimens from my collection, and from the collection of a friend who has a much bigger selection of Mathers specimens than me and noticed that those that fluoresced were generally pretty dim compared to this one.
Its fluorescence under all UV wavelengths is the same color, but brightest under longwave; therefore, it is shown only under LW here.
Originally posted by Frédéric Messier Leroux on Nature's Rainbows in 2021.
Summary of luminescence responses:
Calcite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: White