Caracterização gemológica das ametistas com alta birrefringência de Santa Quitéria

Abstract

Amethyst belongs to the quartz group, is a mineral that can be used as a gemstone and occurs in the violet, lilac and purple colors. These are found in geodes, pegmatites and alluvial deposits. This work aims the gemological characterization of specimens of unstudied amethysts from Santa Quitéria - CE that have high potential to be used as gems; being much appreciated in trade amethysts with red and blue flashes. The gemological characterization of these amethysts was based on refractometer, hydrostatic balance, dicroscope, polariscope, spectroscope, ultraviolet lamp (UV) and gemological microscope. The specimens of the region have mostly the usual gemological characteristics of amethysts from other regions and countries, but with a variation in birefringence and absence of twinning “Lei do Brasil”. Minerals have an excellent color grade, fluid and solid oriented inclusions. Thus, the gemological characterization of these amethysts coupled with the compilation of the available mineral data from this region allowed us to corroborate that these specimens have excellent characteristics to be used as gems.