Gold for jewelry is typically measured in karats – karat definitions are as follows. Note that there can be very little gold in your gold ring.
24 karat Theoretically pure gold – typically 99.9% leaving 0.1% other metals75% gold (ie 25% is not gold)12 karat50% gold9 karat37.5% gold
The above percentages are by weight – since gold is dense compared to other metals, the by-volume percentages of gold in each karat rating are lower. More information is on Wikipedia.
In any case, you can see that most gold jewelry has a significant content of other metals. The crucial issue is then which metals is your gold jewelry alloyed with?
Although ‘standard’ yellow gold may be alloyed with with silver and copper, there is almost no limit to the actual content variations in gold.
Again, this is where an expert (who cares) can truly make the difference between knowing what you have and ending up with an expensive mistake which causes nothing but aggravation and suffering.
White gold is gold alloyed with nickel – which obviously has a potentially high nickel content – although more often than not, “white gold” rings are actually yellow gold plated with Rhodum. The Rhodium wears off in 6 months – 3 years (see below) and needs re-plating. White gold alloyed with nickel is very hard – which makes it much more difficult to ‘work’ into jewelry. Hence white gold is either more expensive than yellow gold… or it isn’t really white gold.
Even white gold alloyed with nickel isn’t pure white – again requiring a rhodium plating to make it appear whiter. An alternative alloying method (which is more expensive and hence less common) is with copper, silver and palladium. This produces a purer ‘white’ and therefore doesn’t need rhodium plating to complete the ‘white’ effect.
Rhodium plating may be applied to white gold jewelry to enhance it’s shine – and in fact to turn ordinary yellow gold into “white gold”.
Although the initial plating will protect you against any nickel in
the gold, the plating is an inherently finite layer over the gold and will wear off. It may even wear off in just a few months leaving the white gold
(alloyed with nickel) in contact with your skin. Bear this in mind when selecting white gold – although it may look great now and may not irritate you
initially, eventually it will wear off. The thickness and quality of plating process will dramatically affect how long this will take to happen but eventually it will
wear off. Needless to say, I hesitate to recommend white gold to anybody with nickel sensitivity.
But which gold has nickel in it?
Gold manufacturers publish data sheets which show which alloys are present in their gold. A jeweler who creates brand new jewelry with new gold will be able to tell you exactly what’s in the gold. Some manufacturers will control the gold and the whole process and will document their jewelry as nickel-free. However since nickel labeling is not required in the US, this practice not common yet.
In order to find true nickel-free jewelry, you need to find a jeweler or retailer who knows enough about their product and it’s origin to guarantee the nickel content. Jewelers and retailers who specialize in nickel-free jewelry are much more likely to be able to help you since they have already dug through the data to know what they are selling.