Manganoan Calcite, Montreal Mine, Montreal, Wisconsin
Contributed by: Chris Clemens
minID: FWX-MYQ
Date: Apr 20th, 2026
Locality: Montreal Mine, Montreal, Gogebic Range, Iron County, Wisconsin, USA (See on Mindat)
Size: 39 x 32 x 45 mm
Weight: 55 g
Description:
This is a manganoan calcite nodule on a goethite matrix, from a location not generally known for producing fluorescent minerals- the Montreal Mine, Montreal, Wisconsin. This multi-wavelength reactive specimen is intensely bright under midwave UV, rivaling the brightest of Franklin calcites. This piece is brightest under midwave UV, followed by the shortwave response. It is least bright under longwave UV.
The Montreal mine was an iron mine located near the town of Montreal, in northern Wisconsin. Production at the mine ceased in 1963. This location is known to produce calcite specimens that show bright fluorescence under UV.
The specimen consists of a hemispheric nodule of light grey/pink calcite (var. manganoan) on a red/brown matrix of limonitic gossan. Although the Montreal Mine has been closed for decades, these specimens are occasionally encountered at mineral shows in the midwestern US.
Originally posted by Chris Clemens on Nature's Rainbows in 2019.
Summary of luminescence responses:
Calcite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Red
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Red
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Red