The different forms of yellow gold can be confusing. This is a layman's guide to the terminology and basic understanding of the different types of yellow gold.
The first thing to understand is the difference between a carat and a karat.
A carat is a unit of measurement. A 6.5mm round diamond is equivalent to 1 carat in terms of measurement.
A Karat refers to the purity of gold, which is what is discussed here.
24 Karat Gold (24K)
24 Karat gold is 100% pure gold with no other metals incorporated into it. Pure gold is very soft and is not used for jewellery manufacture, as a knock could damage and deform a treasured piece of jewellery too easily.
22 Karat Gold (22K)
Many jewellers use 22 arat gold for high quality jewellery items as it is much stronger and durable than 24 Karat. This grade of gold is 92% pure gold and 8% other metals such as silver, zinc and other alloys. It is harder than 24 Karat, but still softer than 18 Karat gold.
18 Karat Gold (18K)
18 Karat gold is made from 75% pure gold and 25% other metals (usually a blend of silver and copper). With white gold, the 25% is made up of white metals to give the jewellery a silver-like colouring.
14 Karat Gold (14K)
14 Karat gold is said to be a happy medium between the beauty of gold and durability. 14 Karat gold is sometimes identified by a 585 stamp, meaning that is is 58.5% pure gold with the remainder a mix of other metals.
9 Karat Gold (9K)
9 Karat gold has a gold purity of 37.5% Because of its low gold content, it is relatively inexpensive and with the higher additional metal content, very durable. Most people cannot visually distinguish between 9 and 14 Karat gold.
Gold plated jewellery is an excellent choice for people who love gold, but cannot afford the price that goes with it. If you like to wear lots of different pieces of jewellery then plating is a good way to build up a relatively inexpensive collection. If you are looking to wear the same piece everyday, then perhaps you need to consider 18 or 22 karat "solid" gold, although this will be more expensive.
Gold plated jewellery is created by using electricity or chemicals to apply a very thin layer of gold over another metal - usually silver, copper or brass.
Gold filled jewellery is created by using pressure to bond a layer of real gold onto another metal. The gold layer that is applied is thicker than plated gold. It won't tarnish or rub off like gold plating will eventually do. This is a great option if you can't afford solid gold, but want something special to wear for many years.