The Many Colors of Gold

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Transcript:
You likely know about many of the different colors of gold such as yellow, white or rose, but you probably haven’t realized just how many different shades of gold there are.

One way the color of gold is changed is by mixing it with other metals. This mixture of metals is referred to as an alloy. Most gold jewelry is formed from alloys. Only 24 K gold is pure. 24 Karats means the gold is 24 out of 24 parts gold or a 100 percent. Whereas 18 karat gold will be 18 out of 24 parts gold or 75%. So what are the other metals that are added to make different colors of gold. Many gold alloys contain copper or silver which can make the jewelry harder since pure gold is surprisingly soft. This graph shows various ratios of copper, silver, and gold and what color they would appear. For example a ratio 1 part silver to 3 parts gold (by weight) will make a green or greenish yellow alloy of gold. This was commonly referred to as Electrum. Using other ratios you can also produce yellow gold, white gold, red gold or rose gold. Other colors can also be made from alloys with different metals. For example spangold is an alloy of aluminum and gold and grey gold can be made with palladium and gold.

Gold can also be reacted with aluminum, gallium, or indium to form compounds that are sometimes referred to as blue gold or purple gold but these are compounds and not alloys. They are much more brittle than real gold and are very rarely used in jewelry.

One last method of producing different colors of gold is by forming oxides of different alloys. By causing the outer layer of certain alloys to corrode, shades of either black or blue gold can be produced, but this color is only forming on the outermost layer.
So, which color is your favorite, and If you would like to see more videos on metals and alloys let me know in the comments below. Thanks for watching.