18 kt gold ring adorned with a 0.06 carat amethyst and 20 zirconium oxides

Gold : Because of the softness of pure gold, it is alloyed with silver, copper or palladium. The proportion of these other metals give yellow, white gold. Without precision, the gold used in jewelry is 18 K, corresponding to 75% pure gold.
Carat : The carat (ct) is a unit of mass equal to 2 g. Carat is used for measuring the weight of gemstones.
Amethyst : Amethyst is a popular form of quartz that ranges from a bright to dark or dull purple color. Heated the color of the amethyst changes to yellow and is then called citrine.