A combinative technique to recognise and discriminate turquoise stone

Abstract

This study attempts to identify and categorize turquoise stone based on its compounds and major factors that introduces its color change. Turquoise samples which are investigated in this study have been collected from the most important turquoise mines in world. Combination of two different analysis methods assists this study for scrutinizing turquoise constituents and effects of their percent on its color change. The application of infrared spectroscopy and X-Ray Fluorescence (XRF) methods can reveal the true composition of various “turquoise” samples in range of blue color to green color. Whereas the first technique (FTIR) is especially capable in diff ;erentiating between natural samples and fake or simulant stones for prevent of jobbery. Changing percent of four compounds including CuO, Al2O3, P2O5 and Fe2O3, is the most effective factors of varying color in turquoise stones. In conclusion, blue turquoise stone contains great percent of light elements or blue color factors in comparison to green turquoise stone which contains jorum of heavy element.