American gold jewellery must be of at least 10K purity (41.7% pure gold), (though in the UK the number is 9K (37.5% pure gold) and is typically found up to 18K (75% pure gold).
Higher purity levels are less common with alloys at 22 K (91.6% pure gold), and 24 K (99.9% pure gold) being considered too soft for jewellery use in America and Europe.
Alternatively, jewellery has been used as a currency or trade good Jewellery can also symbolise group membership (as in the case, of the Christian crucifix or the Jewish Star of David) or status (as in the case of chains of office, or the Western practice of married people wearing wedding rings).
Wearing of amulets and devotional medals to provide protection or ward off evil is common in some cultures.
For many centuries metal, often combined with gemstones, has been the normal material for jewellery, but other materials such as shells and other plant materials may be used.