Four Color Specimen from the Garpenberg Mine, Sweden

Contributed by: Michael Crawford
Date: Aug 3rd, 2025
Locality: Garpenberg Norra Mine, Garpenberg, Hedemora, Dalarna County, Sweden (See on Mindat)
Size: 7 x 11 cm

Description:
A four-color specimen from the Garpenberg Norra Mine, Garpenberg, Hedemora, Dalarna County, Sweden. The specimen contains sphalerite, willemite, fluorite, and calcite. The four minerals generally occur in their own separate band in the specimen. Sphalerite fluoresces orange under longwave and midwave UV light, willemite fluoresces green only under shortwave UV light, fluorite fluoresces blue only under longwave UV light , and calcite fluoresces red only under shortwave UV light. Some of the sphalerite in this specimen does not fluoresce under shortwave UV light like many of the other sphalerites from Garpenberg. Most Garpenberg sphalerites fluoresce under all wavelengths of UV light.

The last picture shows the emission spectra of the minerals in the specimen. The longwave emission spectrum of the sphalerite has two peaks, one at 422 nm and 605 nm. The broad peak at 605 nm is caused by a manganese activator replacing some of the zinc. The 422 nm is caused by fluorite mixed in with the sphalerite. The fluorite peak disappears in the midwave and shortwave spectra of the sphalerite. The fluorescence of the fluorite also disappears under midwave and shortwave UV illumination. Europium activates the blue fluorescence in fluorite. Europium replaces calcium in the fluorite structure. Manganese also activates fluorescence in the willemite replacing zinc and in calcite replacing calcium. The shortwave emission spectrum of calcite shows that the calcite is also fluorescent in the ultraviolet region. It has an emission peak at 312 nm that is activated by lead replacing calcium.