Abstract
Coloured crystals of quartz of gemstone-grade, citrine, amethyst and blue quartz, have been synthesized under hydrothermal conditions ranging 320-330°C and 1000-1500kg/cm2. Conditions for colourations were Fe impurity, K2CO3 mineralizer, Ag-lined autoclave for citrine and amethyst, and Co and Al impurities, NaOH mineralizer for blue quartz. These impurities were added in the forms of metals or metallic oxides. Gamma irradiation was necessary for the final colouration of amethyst. Infrared examinations of natural and synthetic quartz crystals were made in the spectral range 2000-4000 cm-1.
