Manganoan Calcite, Montreal Mine, Montreal, Wisconsin

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 mid wave UV, rivaling the brightest of Franklin calcites. The calcite shows a similar, but less bright response under short and long wave UV. The size of this specimen is 45 x 39 x 32 mm, and it weighs 55 grams.

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 photo montage above shows the multi-wavelength fluorescent response of this unusual calcite specimen from an uncommon midwestern location. This piece is brightest under mid wave UV, followed by the short wave response. It is least bright under long wave UV.

Visible light image of the same specimen, consisting 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.

Orange/red fluorescence under short wave UV (254 nm).

Bright orange fluorescence under mid wave UV (302 nm).

Pale red fluorescence under long wave UV (365 nm). The long wave response is the least bright.

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