Often customers ask the question, what are the benefits of 18 karat gold compared to 9 karat? There’s generally a misconception that 9k is more durable – this is not the case. Here we will quickly run through the pros and cons of each alloy.
Karats, or carats, refer to the pure gold content in gold alloys, and is a measurement of the ratio of gold to other metals in the alloy. Other metals in alloys can include copper, silver and palladium, with small amounts of zinc and iridium.
Gold is a rather soft metal, which is why it's alloyed with other metals to make it harder. However, in normal life applications, 18k gold is perfectly durable due to other metals present in the alloy.
Lower karat gold, such as 9k, is not tarnish-resistant but can be easily polished with a jewellery polishing cloth and look like new again.
Obviously, the higher the pure gold content, the higher the cost - the price difference between 9k and 18k pieces is usually around 60%. Generally, we recommend using 18k gold for important pieces such as engagement or wedding rings, or special jewellery set with precious gems.
9k gold is composed of 37.5% pure gold – hence the gold mark 375 – then alloyed with other metals to produce the desired colour. As there is a smaller gold component and a greater component of other alloys, the metal is less durable than 18ct gold. It will tarnish and corrode more easily, especially when exposed to the wearer’s skin acids over time. However, because of the lower gold content, 9k gold is a lot more affordable. It’s perfect for more casual jewellery pieces and dress rings with large semi-precious gem stones or earrings that have less contact with the wearer’s skin.
18k gold is composed of 75% pure gold and is stamped 750. Because pure gold has more tenacity and flexibility than the other metals it is mixed with, and as it’s the dominant component, this alloy is more durable and is unlikely to corrode and tarnish with normal wear. 18k gold is perfect for wedding and engagement rings and jewellery pieces that are to be worn every day. It’s our preferred metal for precious gems such as diamonds, spinels, tourmalines, opals and sapphires. It’s the more expensive choice, however highly worthwhile for fine jewellery pieces.
In Australia, we typically make jewellery in 9k, 14k or 18k gold. 22k and 24k yellow gold is also used in jewellery, with 24k being 100% pure gold.