What are the differences between yellow gold, white gold, rose gold and white gold?

In the collective unconscious, gold is yellow, isn't it?

And yet we find white, pink and grey gold, and even other colours.

Do you know what differentiates these types of gold?

First of all, let's take a step back in time to understand where gold comes from.

Yes, if we want to go back to its origins, we first have to look up at the sky and go back some 3.8 billion years.

Recent studies have shown that the Earth was probably hit by an incessant shower of meteorites and comets from the various asteroid belts in our solar system, which were somewhat disrupted by the movements of large planets such as Jupiter and Neptune.

According to researchers, this bombardment lasted for at least 100 million years (although some say longer, up to 2 billion years), riddling the Earth and also the Moon with millions of impacts of varying magnitude. 

Year after year, all this rocky debris came crashing down on our young planet, enriching it at the same time with all the metal it was made of. Including gold.

And yes, gold is not created peacefully on Earth like diamonds, for example. 

No, gold requires the occurrence of an event as unique as it is grandiose: the death of a star.

Imagine a massive star, ten times, a hundred times, a thousand times more massive than our sun, reaching the end of its life. 

For billions of years, it has consumed all the elements it can: hydrogen and helium at first, then heavier elements as the lighter elements fuse together. 

But now it has nothing left to burn and is becoming unstable.

Suddenly, under the enormous pressure of all these elements collapsing on its core, it explodes, just as a conventional star would, but on an incomparable, titanic scale. 

It then becomes a supernova, offering a cosmic spectacle so brilliant that it can temporarily eclipse an entire galaxy. 

It is here, in this cataclysmic explosion where the energy is so intense, that the heaviest chemical elements are formed. 

In particular, the almost indestructible yellow metal that humanity has used not only as a currency, but also as one of its most precious commodities: gold.

Now you understand why there are only limited reserves of gold on Earth.

Pure gold or alloy?

When extracted, gold is naturally yellow in colour, so we speak of pure, unalloyed gold, the famous 24-carat gold. 

But as incredible as it may seem, pure gold is easily malleable and in reality, unless it is massive, a fine piece of pure gold tends to deform. 

This is why the gold sold in jewellery is generally an alloy of several metals to ensure rigidity.

Gold is a colourful thing!

As you will have realised, it is through the different alloys used that we obtain different shades of gold. 

In the world of jewellery, we mainly find yellow gold, pink gold, white gold and white gold. 

Here's how they differ in their composition:

• Yellow gold: 75% gold, 12.5% silver and 12.5% copper
• Pink gold: 75% gold, 20% copper and 5% silver
• Grey gold: 75% gold, approx. 15% silver and sometimes palladium
• White gold: This term is generally used to refer to grey gold.
  Before it was regulated, nickel was used in its composition; nowadays, white gold is coated with a thin layer of rhodium.
  However, as this tends to disappear over time, you need to remember to have the operation repeated by a jeweller to maintain the colour.

These alloys are composed of different metals (silver, copper, etc.), the main base always being pure (yellow) gold. 

Different colours of gold

There are other, less common shades of gold that you may come across: green, blue, black and even purple:

• Green gold: 75% gold and 25% silver, also known as electrum when alloyed naturally, it has reflections ranging from yellow to green.
• Blue gold: 75% gold, 24.4% iron and 0.6% nickel. It is the heat treatment of the iron that gives the jewellery its blue colour.
• Black gold: rarely used in jewellery, it can be obtained on a white gold base or with a gold and cobalt alloy followed by a surface treatment with black rhodium.
• Purple gold: 79% gold and 21% aluminium, a fragile and brittle alloy that generally limits its use to inlays.

9, 18 or 24 carats?

Applied to precious metals, the carat corresponds to their purity index.

Pure gold is 24 carats, but as explained above, it is too soft to be worked in jewellery.

18-carat gold is the perfect balance between the amount of pure gold (75%) and the other metals, allowing it to be worked while retaining its rust-proof and non-allergenic qualities. The large amount of gold means that the jewellery has a brighter colour and lasts very well over time, making it ideal for jewellery worn on a daily basis.

9-carat gold is harder than 18-carat gold, because there is less gold and therefore more poor metals. But it is also more brittle. 

Containing more copper and silver, it oxidises more easily and is less shiny.

Finally, if 9-carat gold contains half as much gold as 18k gold (37.5% instead of the minimum 75%), you won't find many sellers who will sell it for half the price...

So, white gold, yellow gold or rose gold, it's a matter of taste... 

It is essential, however, to pay attention to the number of carats in your jewellery.