Introduction to Gold Jewellery
Across history, gold has been prized for its beauty and brilliance. And so perhaps not surprisingly, in many cultures there is an irresistible link between gold and the sun.
Yellow gold and especially yellow gold jewellery is still the world’s favourite colour. However, today gold comes in a very wide range of colours to meet all tastes. In the course of alloying— or mixing pure 24 carat gold with other metals — not only gives the natural, soft, malleable gold greater durability, the process can also be employed to change the colour.
For example, white gold is made by alloying pure gold with white metals such as palladium or silver. Furthermore, it is commonly plated with rhodium, such as to provide a harder surface as well as a more brilliant shine. In recent years, white gold has become by far the favourite selection for wedding bands in the United States.
By adding copper to pure gold, it’s possible to create the popular soft pink complexion of rose gold. In addition, the more outlandish colours, for example, blue and purple, can be created by adding patinas or oxides to the surface of the alloy. There’s even black gold made from adding from cobalt oxide.
Fineness is another key component, a critical factor in giving expression the precious metal amounts in gold jewellery. This expresses the purity of the gold, in parts per thousand. And as a stamp on jewellery, it is typically marked without the decimal point.
This chart shows some examples of the composition of various caratages of gold.
The alloying metal combinations above are standard for those employed by the jewellery industry to arrive at the colour/caratage combinations illustrated. However, but these are not the combinations.
White gold compositions listed here are nickel free. Nickel-containing white gold alloys form a very minor proportion of white gold alloys. Typically, they combine other base metals such as copper and zinc.
The following are the normal standards of fineness:
.375 = 9 carat (England and Canada)
.417 = 10 carat
.583 (.585) = 14 carat
.750 = 18 carat
.833 = 20 carat (Asia)
.999 (1000) = 24 carat pure gold
14 carat should be 583 (14/24 = .583333). However, very many manufacturers have taken up the European practice of making 14 carat gold a little over 14 carat. Such that, the fineness mark is 585 in most 14 carat gold jewellery.
Equally, 24 carat is expected to be 1.0 (24/24 = 1.00). But very often in practice, there can be a small amount of impurity in any gold, so may only be refined to a fineness level of 999.9 parts per thousand. This is stated as 999.9.
Finally, the range of tolerances of purity accepted will vary between markets. In China, Chuk Kam (which is Cantonese for ‘pure gold’ or literally ‘full gold’) and which still accounts for the majority of sales of gold, is defined as 99.0 per cent minimum gold, giving a 1.0 per cent negative tolerance band.