We often see gold expressed in karats (k, kt) or carats (ct). What does this mean?
Firstly, depending on where you are from, the terms ‘karat’ or ‘carat’ can have different meanings. Generally in the US and Canada, ‘karat’ is used to denote the purity of gold, whereas ‘carat’ is used to express the weight of precious stones and pearls. In the UK and Australia, ‘carat’ is the spelling more commonly used to refer to purity of gold OR the weight of precious stones.
What does carat or karat mean for gold?
100% pure gold is expressed as 24 carats. Pure gold is actually a very soft substance, so in order for us to use gold practically in applications like jewellery, gold is often mixed with other metals to make it harder and stronger. These mixtures of gold and metals are called ‘gold alloys’.
When we talk about carats, the number of carats in gold is a measurement of how much of the alloy (out of 24 parts) is made of pure gold. I.e. In 9ct gold, 9 parts out of 24 are made of pure gold. The other 15 parts are comprised of a different metal to enhance the strength of the piece. Similarly, 18ct gold is 18 out of 24 parts pure gold, whereas the other 6 parts is comprised of another metal.