Coloured Gold

Coloured gold – Green Gold
Green coloured gold is also known as electrum, it was known to a group of people called the Lydians who lived in western Anatolia in modern day Turkey in about 680 BC.

Green gold is actually a natural alloy and it is green-ish yellow in colour. If it is made artificially it can be made by adding cadmium and copper will give a light green 18-carat gold. An alloy of gold, silver, copper and cadmium gives a dark green alloy, which is quite attractive, however, the problem with these alloys is that cadmium as a heavy metal is toxic!


Coloured gold – Rose Gold / Red Gold

Mixing copper in with the gold forms a red coloured alloy, the more copper in the alloy the more deep the red colour will become. It was once popular in Russia in the 1800’s.

Today it is popular in Arab countries where it can range from rose to pink to red coloured gold.

Coloured gold – White Gold

One of the most popular of coloured gold is white gold, using made by incorporating the white metals, nickel, manganese and palladium or sometimes a mixture of these metals will turn the gold white.

The use of nickel to make white gold does have issues in that 12% of the population may be allergic and get a skin rashes from nickel, so if you are buying white gold it can be important to know the content of the white gold.

Coloured gold – Grey Gold

Grey coloured gold can be formed from a mixture of gold and palladium; it can also be made by adding silver, manganese and copper to gold in appropriate proportions to give a grey colour.

Coloured gold – Purple Gold

Purple coloured gold is also a possibility formed by a mixture of gold and an inter metallic AuAl2 its chemical structure makes it brittle and it is often machined to be used as a gem rather than for mounting gems or as a decorative metal.

 

Coloured gold – Blue Gold 

Blue coloured gold is formed by a mixture of gold and Indium as an alloy, a variation of blue gold is formed if the gold is annoyed with gallium the bluish hue is lighter in this instance.


Coloured gold – Black Gold

Black coloured gold can be used in jewellery and is obtained by various surface treatments, these treatments are:

• Electroplating using rhodium or ruthenium. Ruthenium gives a harder surface.
• By adding a patina using oxygen or sulphur containing compounds
• Plasma can be used to deposit amorphous carbon on the surface to give a black   finish.Oxidation of gold in a controlled way using cobalt and chromium will also give a black surface treatment.In addition alloys containing gold and cobalt will also develop a black surface if they are heat-treated between 700 and 950°
Carat
Colour
Metal
22ct White Gold Gold 90% , Nickel 10%
Manganese , Palladium
18ct Red Gold Gold 75%  , Copper 25%
18ct Rose Gold Gold 75% , Silver 2.75%
Copper 22.25%
18ct Pink Gold Gold 75% , Silver 5%
Copper 20%
18ct Green Gold Gold 75% , Copper 23%
Cadmium 2%
18ct Dark Green Gold Gold 75% , Silver 15%
Copper 6% , Cadmium 4%
  Grey Gold Gold , Silver , Manganese , Copper
18ct Purple Gold Gold 79% , AuAl2 21%
12ct Blue Gold Gold 46% , Indium 54%
14ct Light Blue Gold Gold 58.5% , Gallium 41.5%