Blue halite colour centre aggregates studied by micro-Raman spectroscopy and X-ray diffraction

Micro-Raman spectroscopy and X-ray diffraction were performed for single crystals of natural blue halite from Kłodawa Salt Mine (Zechstein salt deposit). The samples represented navy blue, blue, purple and colourless NaCl. Unusual concentrations of colour centre aggregates in blue samples were found. $F-R_{1}-(F_{3}),R_{2}-(F_{3})$ bands together with plasmon band and M-band were identified and their populations were estimated. Very intensive Raman band at ca. 200$cm^{-1}$ observed in navy blue and blue NaCl halite samples was assigned as originating from colloid particles. The band is destroyed while sample is heated, what confirms the band assignment.