What does Carat Mean in Gold Jewellery?

Carats are the way of measuring the quality of gold jewellery. You must have all heard of 9 carat, 18 carat and 24 carat gold? Well what exactly is a carat?

To explain this I will have to give you a brief explanation about gold.
24 carat gold is pure gold. This means that the gold is not mixed with any other base metals to form an alloy (a mixture of metals). As precious as it may be, 24 carat gold is rather soft for a metal and doesn’t make particularly strong jewellery. So, it is mixed in a recipe (more about this later) with other metals and ‘diluted’ down to make it stronger.

The optimum level and the one that makes the best gold jewellery is 18 carat gold.
This simply means that 18 parts to six parts are gold (out of 24 parts and equal to around about 75%). So to clarify; If 24 carats (24 parts) is pure, unadulterated gold. Then 18 carats (18 parts) is around 75% pure gold and 25% other metal for hardness.
So with this in mind we can easily work out that one single carat is 1/24th of the metal.

So if alloys make gold harder and longer lasting whys is 18 carat better than say 9 or 14 carat?
Answered simply; the durability of 18 carat gold is greater than that of 9 carat gold.
To explain what I mean by durability imagine holding up two spheres, one made of glass which is harder than the other made of rubber.
Dropped from a height, the rubber sphere will bounce but the hard glass sphere will shatter. 18 carat gold is more durable than 9 carat gold and doesn’t break as easily.

Another good reason for choosing 18 carat gold over 9 carat gold is that 18 carat is almost completely resistant to attack from normal chemicals. 9 carat gold however, will go dull in colour and even turn black when it is exposed to chemicals in the atmosphere. This can also happen with contact to perspiration and household cleaning products.

The ‘recipe’ alloy that gold is mixed with is a combination of different metals to form an alloy. Different metals have different properties that can be altered by rolling and stretching to become harder (but more brittle) and heating (annealing) to different temperatures then cooled in certain ways to soften the metal to just the right durability. This process is individual to master jewellers and can make the difference in the quality of the jewellery that they produce.

The method for measuring the way that an alloy (pure gold is a metal too, and when mixed with other metals it is classed as an alloy) is by using the Vickers scale.


This is explained more HERE.

I hope this helps you when you go to choose new jewellery or you are trying to sell scrap jewellery. Try HERE for that - best prices we've found.

I enclose a video by new band Johnossi call 18 Karat Gold. This is really quite good.
http://www.youtube.com/watch?v=tnju3KTRh5A