about gold

Gold Jewellery
Throughout history, gold has been treasured for its natural beauty and radiance. For this reason, many cultures have imagined gold to represent the sun.
Yellow gold is still the most popular colour, but today gold is available in a diverse palette.
 
Gold Purity
Fineness is another way of expressing the precious metal content of gold jewellery, and represents the purity in parts per thousand. When stamped on jewellery, usually this is stated without the decimal point.  

This chart shows some examples of the composition of various caratages of gold.
Colors Caratage Gold(Au) Silver (Ag) Copper (Cu) Zinc (Zn) Palladium (Pd)
Yellow Gold 9k 37.5% 42.50% 20%
Yellow Gold 10k 41.70% 52% 6.30%
Yellow Gold 14k 58.30% 30% 11.70%
Yellow Gold 18k 75% 15% 10%
Yellow Gold 22k 91.70% 5% 2% 1.30%
White Gold 9k 37.5% 62.5%
White Gold 10k 41.7% 47.4% 0.9% 10%
White Gold 14k 58.30% 32.20% 9.50%
White Gold 18k 75% 25% (or Pt)
White Gold 22k N/A N/A N/A N/A N/A
Rose Gold 9k 37.5% 20% 42.5%
Rose Gold 10k 41.70% 20% 38.3%
Rose Gold 14k 58.30% 9.2% 32.5%
Rose Gold 18k 75% 9.2% 22.2%
Rose Gold 22k 91.7% 8.40%
Colors Caratage Gold(Au) Silver (Ag) Copper (Cu) Zinc (Zn) Palladium (Pd)
Yellow Gold 9k 37.5% 42.50% 20%
Yellow Gold 10k 41.70% 52% 6.30%
Yellow Gold 14k 58.30% 30% 11.70%
Yellow Gold 18k 75% 15% 10%
Yellow Gold 22k 91.70% 5% 2% 1.30%
White Gold 9k 37.5% 62.5%
White Gold 10k 41.7% 47.4% 0.9% 10%
White Gold 14k 58.30% 32.20% 9.50%
White Gold 18k 75% 25% (or Pt)
White Gold 22k N/A N/A N/A N/A N/A
Rose Gold 9k 37.5% 20% 42.5%
Rose Gold 10k 41.70% 20% 38.3%
Rose Gold 14k 58.30% 9.2% 32.5%
Rose Gold 18k 75% 9.2% 22.2%
Rose Gold 22k 91.7% 8.40%
Notes:
The alloying metal compositions above are typical of those used by the jewellery industry to arrive at the colour/caratage combinations shown, but these are not the only ways to arrive at these combinations.
White gold compositions listed here are nickel free. Nickel-containing white gold alloys form a small/very small percentage of white gold alloys and generally contain other base metals such as copper and zinc.
 
The following are the common standards of gold fineness that are used:
9 carat

375 (37.50%)

10 carat

417 (41.70%)

14 carat

583 (58.33%)

18 carat

750 (75.00%)

24 carat pure gold

999 (99.99%)

24 carat pure gold

999 (99.99%)

24 carat pure gold

999 (99.99%)

9 carat

375 (37.50%)

10 carat

417 (41.70%)

14 carat

583 (58.33%)

18 carat

750 (75.00%)

20 carat pure gold

83.3%

22 carat pure gold

91.6%

24 carat pure gold

999 (99.99%)

Strictly speaking, 14 carat should be 583 (14/24 = .583333), but most manufacturers have adopted the European practice of making 14 carat gold slightly over 14 carat. Thus, the fineness mark is 585 in most 14 carat gold jewellery.

Similarly, 24 carat should be 1.0 (24/24 = 1.00). However, in practice, there is likely to be a very slight impurity in any gold, and it can only be refined to a fineness level of  999.9 parts per thousand. This is stated as 999.9.
Accepted tolerances on purity vary from market to market. In China, Chuk Kam (which is Cantonese for ‘pure gold’ or literally ‘full gold’) still comprises the majority of sales and is defined as 99.0 per cent minimum gold, with a 1.0 percent negative tolerance allowed.