Sphalerite spectroscopy

 

Spectroscopic techniques are widely used nowadays in gemmological laboratories for gems identification and characterization. In this section we publish UV-Vis-NIR, Raman, Photoluminescence and FTIR spectra collected for ten Spanish sphalerite samples of different colors in the Gem Testing Laboratory of the Spanish Gemological Institute.

 

samples for sphalerite spectroscopy study

Ten samples of brilliiant cut sphalerites with different colors, form yellow to dark reddish orange,
used for this study. Diameters 7.1-8.3 mm, weights 1.85-2.92 ct. 

 

sphalerite optic absorption spectra 

Optic absorption spectra of ten Spanish sphalerites, collected on GemmoSphere spectrometer. (Click to enlarge).
Note how the absorption border is shifting from left to right from yellow-colored through oranges to reddish sphalerites, closing more and more the transmission window and thus limiting the dispersion observed in more reddish samples. This figure explains why in lightly colored yellow sphalerites the dispersion causes flashes of different colors, while in reddish stones almost all colors but red and orange are absorbed, so very low dispersion can be seen.
 

 

sphalerite raman spectra 

Raman spectra of ten Spanish sphalerites, collected on GemmoRaman-532SG spectrometer. (Click to enlarge).
The variation in peaks intensity can be caused by different orientation of the facet used for analysis (table) in each sample with regards to its crystallographic orientation.

 

sphalerite raman spectra different orientation 

 Raman spectra of the same sample of Spanish sphalerite (stone #1), collected with different orientations of the sample. Four spectra are collected on the table facet and other four on different facets of the pavilion. This figure shows the dependence of the Raman peaks intensity on the sample orientation.
GemmoRaman-532SG spectrometer. (Click to enlarge).

 

 sphalerite photoluminescence spectra

Photoluminescence spectra of ten Spanish sphalerites, collected on GemmoRaman-532SG spectrometer.
(Click to enlarge).

 

 spanish sphalerite ftir spectra

FTIR absorption spectra of ten Spanish sphalerites, collected on GemmoFTIR spectrometer. (Click to enlarge).

 

ftir specular reflection spectra

FTIR specular reflection spectra of ten Spanish sphalerites, collected on GemmoFTIR spectrometer.
(Click to enlarge).