Precious Stones - Chemical Composition and Colours

Stone Colour Chemical Composition
Diamond Transparent Carbon
Ruby Pink to Red Corundum (Aluminium oxide Al2O3)
Emerald Green Beryl (Be3Al2(SiO3)6)
Sapphire Blue Corundum (α-Al2O3)
Amethyst Violet Quartz (Silicon dioxide SiO2)
Opal Variety of colours Hydrated silica (SiO2·nH2O)
Turquoise Blue to greenish Hydrated copper and aluminium phosphate [CuAl6(PO4)4(OH)8·4H2O]
Topaz Variety of colours Aluminum silicate containing fluorine (Al2(F,OH)2SiO4)
Lapis Lazuli Deep blue Metamorphic rock with mineral lazurite as its chief constituent
Aquamarine Pale greenish blue or bluish green Beryl (Be3Al2(SiO3)6)
Morganite Pink to orange-pink Beryl (Be3Al2(SiO3)6)
Onyx Bands of black and white Silicon dioxide (SiO2))

Other Precious Materials

Material Colour Chemical Composition
Pearl White (other colours are also possible but rare) Argonite (Calcium Carbonate CaCO3))
Ivory White Dentine (Ca10(PO4)6(CO3)·H2O))