Four Color Specimen from the Garpenberg Mine, Sweden

Contributed by: Michael Crawford
Date: Aug 4th, 2025
Locality: Garpenberg Norra Mine, Garpenberg, Hedemora, Dalarna County, Sweden (See on Mindat)
Size: 8 x 18 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 occur in their own separate band in the specimen. Sphalerite fluoresces orange under all wavelengths of UV light. It is the only mineral to fluoresce under midwave light. Willemite fluoresces bright green under shortwave UV light and is weakly fluoresces green under longwave UV light. Fluorite fluoresces blue only under longwave UV light. Calcite fluoresces red only under shortwave UV light.

The last image shows the emission spectra of the minerals in the specimen. The longwave emission spectrum of the sphalerite has two peaks, one at 421 nm and 598 nm. The broad peak at 598 nm is caused by a manganese activator replacing some of the zinc. The 421 nm peak is caused by fluorite mixed in with the sphalerite. Europium activates the blue longwave 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 willemite spectrum peaks at 519 nm and the calcite peaks at 614 nm