Many believe, including some jewellers, that the higher the carat of gold the softer the metal (gold is a soft metal). Therefore 9 carat gold, being alloyed with other metals tends to be more resistant to scratching than say 22 carat gold. This is not necessarily the case. Many manufacturers producing 18 carat gold jewellery ensure that, as the jewellery is higher quality, the alloy is harder wearing. This way when you have bought a piece of fine jewellery it will last a long time.
White gold and rhodium plating
Pure gold is yellow in colour but to satisfy the demand for white precious metals ‘white’ gold alloys can be produced by alloying yellow gold with naturally white precious metals such as palladium or silver, or non-precious ‘white’ metals to reduce the yellowness of the resulting alloy. Gold bullion suppliers now sell a range of graded white gold alloys which can be compared against a published scale of “whiteness”. However, white gold is routinely electroplated with Rhodium, a precious white metal which imparts a bright white finish. Depending on the level of wear, this finish wears off and white gold thus requires more care and maintenance to keep it bright.
If the underlying white gold is a yellower grade then it will start to show through as the rhodium wears. Consumers should bear in mind that their white gold jewellery may require re-plating at variable intervals depending on the amount of wear and the thickness of rhodium plating which can be applied to the jewellery. Some designs, particularly those with sharp edges and corners, may only be suitable for a thin plating of rhodium.
Red and other colours of gold
Red or rose gold is created by increasing the amount of copper in the alloy. Introducing other metals (or removing them completely) can make other colours of gold, including unusual tones such as green and blue but these are not generally available.