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Chemical characterization and chromophore elements in elbaites from Borborema Province, Brazil

Tourmalines from the Borborema Pegmatite Province were investigate in order to correlate different colors of tourmalines and possible chromophore elements. Chemical composition of blue, green, pink and turquoise tourmaline were determined by EMPA, using internal standards previouslyanalyzed by ICP-MS. All analyzed samples are elbaite, according to their chemical composition. ICP-MS data show small, but significant variations in chemical composition. Different colors can be correlated with several elements or even combination of these elements, such as common chromophores Fe, Mn, Cu and Ti. The blue coloration could be a result of intervalence charge transfer connected to Fe content. Combination of homonuclear intervalence charge transfer (Fe2+ - Fe3+) combined with low Cu concentration produce the blue coloration of "Paraiba" tourmaline. Higher concentration of Cu change the color towards green and tourquoise. The pink/red color seems connected with Mn content.

elbaite; Borborema Pegmatite Province; chromophore elements; EMPA; ICP-MS

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