Pure gold is used more for investment than decoration, as it tends to be quite vulnerable to scratching. Elsewhere, it is usually mixed, or alloyed, with other metals. This not only hardens it, but also influences the colour; white shades are achieved by alloying gold with silver, nickel or palladium, while red alloys mainly contain copper. You can make an alloy harder by adding nickel, or a tiny percentage of titanium.

The most widely used alloys for jewellery in Europe are 18 and 14 carat, although 9 carat is popular in Britain. Portugal has a unique designation of 19.2 carats. In the United States, 14 carat is the most popular density, followed by 10 carat. In the Middle East, India and South East Asia, jewellery is traditionally 22 carat (sometimes even 23 carat). In China, Hong Kong and some other parts of Asia, chuk kam or pure gold jewellery of 990 fineness (almost 24 carat) is popular.

In many countries, laws require that every item of gold jewellery be clearly stamped with its caratage. This is often controlled through hallmarking, a system which originated in London at Goldsmiths' Hall in the 14th century. Today, hallmarking is compulsory in such countries as Britain, France, the Netherlands, Morocco, Egypt, and Bahrain. But even where there is no compulsory marking, manufacturers usually stamp the jewellery themselves both with their own individual identifying mark and the caratage or ‘fineness’.

The European Commission wants to introduce a common system for guaranteeing standards of fineness. There are three possible systems for this:

1. Hallmarking.
2. Quality control, according to the European norm on quality (EN 29000).
3. Certificate of conformity by manufacturers, control-led by an independent third party.

Want to know more?   This table provides the various karatages and their equivalent gold content in percentage and fineness terms, as recognised by international standards which you might find useful.

 

Definition of karatage in gold content for recognised international standards

 

Carats / Karats	Fineness (of 1000)	Gold, % content	Comments
24	999	99.9%	Pure gold
24	990	99.0%	Minimum allowed for pure gold
22	916	91.6%	Indian subcontinent
21	875	87.5%	Arabic countries
(19.2)	800	80.0%	Standard in Portugal
18	750	75.0%	Standard international Karatage
14	585	58.5%	583/58.3% in USA
10	417	41.7%	Minimum in USA
9	375	37.5%	U.K. standard
8	333	33.3%	Minimum Germany