Please note that the results here represent a development in techniques and processing methods. The Praborna material was the first spectrum taken with entire manual processing while the spectra on the Cleuson site are more recent with optimized procedures. All results shown here are made with the first version of the spectrometer which had a lower resolution and a higher noise level than the actual one.
Praborna, Aosta, Italy
Praborna(z) is a famous manganese mine with a huge variety of minerals. An extensive search of the mine with a powerful shortwave UV-lamp revealed a white mineral with a strong yellow fluorescence. A literature database search gave no information about fluorescent minerals from the Praborna mine, therefore this sample was chosen for the first real live test of the system. The unknown mineral turned out to be powellite:
What black box systems don't show you: the pre-processed spectrum image with the ImageJ profile plot. First line from left is the laser line:
And the screenshot from CrystalSleuth: black line: this sample, blue line: Rruff reference for powellite at 532 nm. Note the peak at about 100 cm-1 showing the excellent quality of the Semrock filter:
The first test with an unknown mineral already provided interesting informations as powellite was previously not reported from Praborna (to the best of my knowledge).
Since Praborna is a quite interesting mine, let's stay there. Another interesting question is about the nature of "violan" found in the mine. According to literature two violan varieties can be found at Praborna, One is P2/n omphacite, the other disordered C2/c impure diopside, both contain small amounts Mn-ions responsible for the violet color (see Mineralogy and Petrology 26 (1979) 187-201). The specimen below is about 9 cm wide and in this case the violan consists of omphacite.
And again the screenshot from CrystalSleuth: black line: this sample, blue line: Rruff reference for omphacite at 532 nm.
The spectrum was taken from a small chip of a dark violet section of the specimen.
Further examples for micro raman spectroscopy can be found at the Cleuson and Lainejaur sites.