Gold is a noble metal. It is a beautiful metal for use in jewelry and has an old tradition….Gold is about as soft as lead and is easily scratched. ……….. For some jewellery, a gold alloy is used, the most common being 18k, with 24k being entirely pure. 18k gold contains 75% gold and 25% copper and silver. Traces of other metals may also be present. In lower quality gold, zinc and nickel can also be found….. Allergy to gold is uncommon but it does exist, and then mostly from white gold. In some extreme cases, the copper in the jewelry can "bleed" out and cause greenish discolorings to the tissue….