COLOR CHANGE of TURQUOISE-COLORED COPPER SILICATE MINERALS EXAMINED by CHEMICAL, PHASE and MICROSTRUCTURE ANALYSIS

Abstract

In nature, copper silicate minerals generally have a turquoise color between the blue and green color spectrum. Turquoise color tones may vary depending on the stoichiometry and crystal structure in these minerals. In this study, the variation of color tones in copper silicate mineral with different turquoise colors was investigated. The causes of color change were investigated by chemical and mineralogical analyzes of copper silicate mineral in four different tones. Turquoise color becomes more vivid visually with increasing CuO and decreasing SiO2 ratios. With changing stoichiometry, the crystal lattice parameters also change. The turquoise color of the minerals containing the highest (~16%) CuO and the lowest (~70%) SiO2 has the best visual appearance compared to the others. For the same sample, the crystallite size was observed as 171 Å, which is the smallest crystallite size among the samples. In addition, SEM images and EDX analyzes of these samples were made and they were found to be consistent with mineralogical analyzes.

Keywords

• Copper Silicate
• Turquoise
• Color
• Mineral

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