White gold

White gold is a gold alloy in which gold is mixed with one or more pale-coloured metals to give the alloy a light appearance. The precise composition varies. White-gold jewellery is often rhodium plated for a brighter white surface; rhodium plating is a surface coating and does not change the gold content of the alloy.

Colour alone does not establish metal content or fineness. The carat or fineness mark refers to the gold proportion: 18 carat normally means 750 parts per thousand gold, whether the alloy is white or yellow. See fineness and fineness marks and X-ray fluorescence (XRF); a surface XRF reading may be affected by coatings and must be interpreted with that limitation in mind.

Sources: World Gold Council, Gold Jewellery: Colour, Carat & Purity; Sheffield Assay Office, Is your plating breaking the rules?.