Red Fluorescent Sphalerite from the Huanzala Mine, Peru
Contributed by: Michael Crawford
Date: Sep 17th, 2025
Locality: Huanzala Mine, Huanzala, Huallanca District, Bolognesi Province, Ancash, Peru (See on Mindat)
Size: 6.5 x 8.5 cm
Description:
A specimen with orange and red fluorescent sphalerite (ZnS) from the Huanzala Mine, Huallanca District, Bolognesi Province, Ancash, Peru. The fluorescence is brightest under longwave UV illumination. It is dimmer under midwave and shortwave light. Longwave emission spectra of the red fluorescent sphalerite show that the fluorescence is significantly brighter in the near infrared. There are two types of red fluorescent sphalerite in this specimen. One type (#2) has two broad peaks with maxima at 731 nm and 859 nm. There is also a sharp peak at 832 nm. Th second type (#1) also has two broad peaks, but the peak at 712 nm is much less intense compared to the second peak at 876 nm.
Copper replacing zinc is part of the activation of the red and near infrared fluorescence. However, different co-activators must also be present to cause these two different emission spectra in the near infrared. Red fluorescent sphalerite from Montana and Pennsylvania have longwave emission spectra that present two more signatures of near infrared fluorescence. These four spectral signatures indicate at least four different co-activators. Recent research shows that tungsten and copper is responsible for the red fluorescence of the Montana sphalerite. Glenn Waychunas described in the 2020 FMS Journal that the red fluorescence of the sphalerite is activated by copper along with nearby vacancies of sulfur atoms in the ZnS crystal lattice. There is no mention of the source of this sphalerite or if it also creates near infrared fluorescence. Fluomin lists Cu+-Ga3+ and Cu+-In3+ replacing Zn2+ activating red fluorescence. Again, no information is given for the source of the material with this activation or if it also causes near infrared fluorescence.
The specimen also contains two types of orange, fluorescent sphalerite. Both have emission peaks at 584 nm. This orange fluorescence is activated by manganese replacing zinc. One type (#3) of the orange fluorescent sphalerite also has fluorescence in the near infrared with a peak at 876 nm. It is unknown what the activator might be for this near infrared fluorescence.
A false color image of the near infrared fluorescence shows the four different types of sphalerite. The false color image is a composite of three monochrome images taken with narrow bandpass filters (720 nm, 770 nm and 860 nm) shown on the spectral plots. The false color image is created by assigning the 860 nm image to red, assigning the 770 nm image to green, and assigning the 720 nm image to blue. These numbers correspond to the numbers on the annotated image and spectral plots.
Type 1 is red to pink in the false color image and dark red in the true color image
Type 2 is light blue to white in the false color image and bright red in the true color image.
Type 3 is orange in the false color image and orange in the true color image.
Type 4 is black (non-fluorescent) in the false color image and orange in the true color image.
Summary of luminescence responses:
Sphalerite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Red
- Fluorescence under Longwave (365nm LED) UV light: Orange