Importance of Carat in Gold Jewellery

Carat, the means for measuring the quality of gold jewelry. You must have all heard of 9 carat, 18 carat and 24 carat gold?
24 karat gold is pure gold. This means that gold is not mixed with other metal alloy (a mixture of metals) to form. As valuable as possible, 24-karat gold is quite soft for a metal and is not particularly strong jewelry. So it is mixed in a recipe (more on that later) with other metals and "diluted" by the strongest.
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 why is 18 carat better than 9 or 14? simply; the durability of 18 carat gold is greater than that of 9 carat gold.

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.