Most people are aware that gold is available in different carats and that a difference in carat implies a difference in price, but not many people are aware of what carat means in terms of the metal itself.
Gold alloys for jewellery are made up of a percentage of pure gold and a percentage of other metals such as copper, silver and palladium. The carat rating of an alloy refers to the percentage of gold in the alloy:
9ct = 37.5% gold and 62.5% other metals
10ct = 41.7% gold and 58.3% other metals
14ct = 58.3% gold and 41.7% other metals
18ct = 75% gold and 25% other metals
22ct = 91.6% gold and 8.4% other metals
24ct = 100% gold
This is the traditional "gold" colour that most people envisage when thinking about gold. Most yellow gold items have copper and silver added to the gold in the various ratios listed above. The copper provides additional strength while the silver counteracts the pink tinge of the copper. In Australia, we typically use 9ct and 18ct yellow gold for jewellery. 22ct and 24ct yellow gold offers a beautifully rich yellow due to its purity but is also softer and may not be suitable for all types of jewellery.
As the name suggests, white gold is a gold alloy with a white tone. In order to achieve this colour, a small amount of copper is combined with a significantly higher amount of silver, palladium, or other white metals. White gold is actually a grayish tone in its natural state but when plated with rhodium, the finish is much whiter. In Australia, white gold is most commonly available in 9ct and 18ct.
Pink Gold (Rose Gold)
While weighting the alloy ratio towards silver (or other white metals) makes white gold, weighting the ratio towards copper makes pink gold. Pink gold, as the name suggests, has a lovely, warm, pinkish tone which is particularly suited to designs with an antique style or to people with fair skin tones.
Due to the additional copper in the alloy, pink gold is the strongest of the gold options. While the additional copper strengthens the ring, it also results in a greater difference in appearance amongst the various carats: 18ct pink gold tends to be much subtler in its rosy hue than 9ct pink gold due to the higher gold to copper ratio, 9ct pink gold can be a bit darker in colour as the higher copper ratio reduces the golden luster and 14ct pink gold sits somewhere in the middle and can be a good in-between option.
For most people, this is the leading choice for jewellery, especially engagement and wedding rings. Platinum is a very pure and rare metal with a sturdiness that stands above all other precious metals. It is also the whitest of all the precious metals. Its strength makes it particularly good for the setting of diamonds and other gemstones but it is still susceptible to dents and marks so care must always be taken.
The density of platinum gives a piece a feeling of solidity and quality which many people find pleasing. When polished, Platinum produces an extremely high lustre. In terms of alloy, platinum is used as an almost pure metal - it is typically hallmarked with the number "950", indicating that the platinum is 95% pure. Platinum is currently the most expensive of all the the precious metals.
Sterling silver is an alloy comprising 92.5% silver and 7.5% other metal. The tone is pure white and it can achieve a high shine. It is easy to work with due to its relative softness and it's also an affordable metal when compared with gold & platinum.
Sterling silver can be oxidised to give an antique appearance or even an all-over, black finish. This treatment is semi-permanent and designed to fade over time. The effect can be very pleasing when in combination with certain stones and other surface treatments.