Title : Linking between color and element concentration for Fluorite: An optical spectroscopic approach
Abstract:
The cause of color in fluorite has been studied by mineralogists in the interest of aesthetics to link the geochemistry of specific mineral deposits, and their application as lasers. The color of fluorite minerals has been connected to the existence of defect centers, structural faults, impurity ions, REE-associated defect centers, and the presence of a transition group of elements in fluorite. All these components impact the fluorite hue, and an attempt has been made in this work to link the color of Amba Dongar fluorite in India with rare earth elements and transition elements concentration. UV-visible, fluorescence, and photoluminescence spectroscopic analysis was used to characterize eight fluorite samples of different colors, while element concentration data from ICPMS was used to link the same. UV-visible absorption spectroscopy of all the fluorite samples clearly demonstrated that when higher absorption is observed between 300 to 560 nm wavelength compared to higher wavelength (? 560 nm), shades of yellow color fluorite are evident, which may be correlated to higher Sr concentration. Lower absorption between 560 to 580 nm represents shades of purple and blue color fluorite, which may be due to the presence of Ca- colloids and high Yttrium concertation. Overall flat absorption throughout the visible wavelength, is resulted from the colorless fluorite samples. Emission spectra acquired in Δλ (50 nm) mode of all the fluorite samples showed more or less similar emission peaks due to the presence of eight REE Ions. Detail analysis clearly indicated that the dark yellow color is due to the presence of Tb3+, and the light-yellow color is due to the presence of Dy3+, Ce3+, Ho3+, Er3+, and Gd2+, while blue and purple color is resulted due to the presence of Eu3+. Photoluminescence spectroscopy of yellow fluorite show emission at different wavelength due to the presence of Dy3+ and Er3+, while blue and purple fluorite showed emission due to Sr2+, Er2+. Sr concentration is less in purple and colorless fluorite, while it increases from light yellow to dark yellow, as evident from ICP-MS data. The total REE concentration of all the samples doesn’t show much variation in all the fluorite samples.
Keywords: Fluorite, Optical Spectroscopy, Amba Dongar, Color variation, ICP-MS, REE.
Audience Take Away:
UV-visible, fluorescence, and photoluminescence spectroscopy examination was utilized to describe eight fluorite samples of varying hues, while element concentration data from ICPMS was used to connect the same.
comprehending why these components affect the fluorite hue, where an attempt has been made in this work to link the color of Amba Dongar fluorite with rare earth elements and transition elements concentration.
