Red gold, green gold, white gold … : All about coloured gold alloys

Red gold, green gold, 18 carat gold, 750 gold … So many differences ! Why so many different types of gold ? Whys isn't pure gold that is used in jewellery ?

We all have some gold at home. It can be jewellery, coins or even bullion for the luckiest of us. However jewellery is rarely made of pure gold. Contrary to what one could expect, the main reason is not the cost.

Sure, a piece of jewellery made of pure gold would be more expensive than for example another made of 75% gold and 25% some other metal.

However, should you know the margin that your favourite jeweller makes, it really wouldn't change much of the final price.

Actually 24K (pure gold) jewellery exists, it is rather popular in China and Hong Kong. In Europe or in the USA, it is much rarer.

What is made of pure gold is usually bullion and investment coins.

Why is our jewellery not made of pure gold ?

Coins and jewellery are generally not made only of gold. Indeed, they are created to be worn or used on a daily basis.

A piece of jewellery made of pure gold is too soft and would change of shape if worn frequently.

This is the main reason why jewellers add other less noble metals to their creations.

For example a 750 ring is made of 75% pure gold and 25% of something else. That other metal will change the colour of the piece of jewellery ; this is why we speak of coloured gold

What is the number of carats ?

For diamonds, the Karat (yes, with a 'k') is a unit of weight. But for gold it is completely different. The carat is a unit of purity. The maximum value is 24, meaning that the piece of jewellery is only made of gold.

A 18 carat necklace is therefore made of (18/24 = 0.75) 75% of gold and some other 25% of some other metal.

A 14 carat ring is made of (14/24 = 0.5835) 58.35% of gold and some other 41.75% of some other metal.

A 9 carat chain is made of (9/24 = 0.375) 37.5% of gold and some other 62.5% of some other metal.

Yes, you have read correctly, it is possible to buy a ring/chain/necklace in 'GOLD' that is not really in gold because only a third of it is really gold.

It shouldn't be a surprise to you that the cheapest jewellery you will find will be in 9 carat. It is forbidden to says that the piece of jewellery is a gold one if there is less than 37.5% of gold in it.

(Ok there is even cheaper than 9 carat: gold plated : only a extremely thin layer of gold is applied on the surface of the piece of jewellery, which core is entirely made of another much cheaper metal).

What are the colours of gold ?

Yellow gold

Yellow gold is made of gold, silver and copper. For 18 carats jewellery, we need 75% of gold, 12.5% of silver and 12.5% of copper to get this beautiful yellow colour.

Most of the jewellery is yellow gold. Usually when people think about jewellery they think yellow gold.

Pink gold

Pink gold is composed of the same metal than yellow gold but not in the same proportions.

For 18 carat jewellery, there is still 75% of gold, but 20% of copper and only 5% of silver.

The pink colour comes from the greater proportion of copper. Speaking of copper ...

Red gold

From yellow to pink, the next step is obviously red gold !

I think you can guess what metal makes jewellery red... Congratulations : you guessed correctly !

Red gold is made of gold and copper only. Therefore, for 18 carat jewellery, 75% gold and 25% copper.

Similarly, for 9 carat red gold, 37.5% gold and 62.5% copper.

White gold

White gold, also called grey gold (sorry, nothing related to the lord of the Rings... it is Gandalf the grey, not Goldalf the grey), is made from gold, silver and palladium.

Please note that ancient jewellery can contain nickel instead of palladium, because nickel is way cheaper than palladium. It turned out that the nickel in the alloy could cause some allergies, itching when in contact with the skin. (and surprisingly, rings are usually in contact with the skin...).

For this reason, nowadays, nickel is rarely used in White gold.

Green gold

Green gold is not some kind of vegetable or any eco-friendly new type of oil. It could be though...

For jewellers, green jewellery is made of Gold and Cadmium. For 18 carat jewellery, 75% gold, 15% silver, 6% copper and only 4% cadmium.

Green gold was called Electrum in ancient time by the Greeks (Lydians) as a natural alloy of gold and silver (and cadmium in small quantities). It is good to know should you be teleported back 2500 years ago and want to buy some nice jewellery.

It is a rather rare alloy because there are health issues with alloys in green gold because the cadmium is highly toxic.

Purple gold

Purple gold is not made of purple rain. No, it is an alloy made of Gold and Aluminium.

It is called Amethyst gold by some marketers eager to sell it under a rather pretty name but is more brittle than gold and therefore not used very often.

There are different variants of purple gold base on the amount of aluminium.

Blue gold

At last, blue gold... Blue gold is made of Gallium or Indium and Gold. It is a rather pretty sight

Another way to produce blue gold jewellery is to use Iron and Gold. (I wonder if corrosion will make it change colours).

Black gold

Black gold is obtained with a surface treatment by applying sulfur and oxygen containing compounds. there are other processed to produce black gold such as Plasma-assisted chemical vapor deposition process involving amorphous carbon or Controlled oxidation of gold containing chromium or cobalt.

What colour is the most expensive ?

Most scrap gold buyers will smelt jewellery to extract the gold in them and discard other metals. Consequently, the colour of the piece of jewellery is not important and has no influence on the price they can give you for your jewellery.

One could think that white gold could bring more money because there is silver and palladium. However, do not forget that the price of a gram of gold is roughly between £30 and £40 whereas a gram of silver is less than 1£.

Of course there are some exceptions : some jewellers will directly resell jewellery and in such cases, the beauty of the piece of jewellery is of utmost importance.

You can check out our guide to get more for your now unwanted jewellery

Cheap and low cost jewellery

This shouldn't be a big surprise to you : cheaper jewellery means less gold. Have a closer look at the description, if it is 9 carats or 375, there is half as much gold as in 18 carats or 750 jewellery !

One could expect that 9 carat jewellery be half price of what 18 carat jewellery sells. After all, there is twice as much gold in 18 carat than in 9 carat.

However, the difference in price, though it exists, is rarely 50% but a little less. So yes, cheaper 9 carat jewellery is cheaper than 18 carat, but from a pure quality/price point of view, you will get a better ratio with 18 carat jewellery than with 9 carat.