Bague en or jaune 18 ct 1 topaze

Yellow gold : Yellow 18K gold is an alloy contianing 75% of pure gold, whereas 14K gold contains only 58,5% of pure gold.
Carat : The carat (ct) is a unit of mass equal to 2 g. Carat is used for measuring the weight of gemstones.
Topaz : Topaz is a silicate mineral of aluminium. Imperial topaz is yellow, pink (rare, if natural) or pink-orange. Brazilian Imperial Topaz can often have a bright yellow to deep golden brown hue, sometimes even violet. Many brown or pale topazes are treated to make them bright yellow, gold, pink or violet colored. Naturally occurring blue topaz is quite rare. Typically, colorless, gray or pale yellow and blue material is heat treated and irradiated to produce a more desired darker blue.