Many people are interested in how to test gold for purity. But how pure can you expect gold jewellery to be in reality? And how can you find out a jewellery item's actual gold content? Let's see what works in gold purity testing and what doesn't.
It is commonly accepted that gold that is not mixed with other metals is referred to as pure.
The purity of gold is usually measured in karats. 24 karats is the highest purity possible and corresponds to about 99.9% gold content.
Pure gold is very soft and malleable, and has an intense yellow color.
Because of its softness, pure gold is rarely used to make jewellery.
Items made of 24K gold bend very easily, and this is why pure gold is not a good choice for pieces that will be worn as adornment.
Not to mention that any settings made of pure gold would wear out pretty quickly, making it easy for any stones in them to fall off.
The gold that is used to make jewellery is actually a gold alloy - a mixture of pure gold and other metals, which are added in to make the alloy harder.
So, almost all gold jewellery is not actually pure gold.
Usually, gold jewellery comes with markings stamped on it that indicate what its karat is. If there are no marks or if you just want to check whether the gold is as pure as it is claimed to be, you can test it.
There are different methods, but the most reliable one is acid testing.
You can have your gold tested for purity at most jewellery stores.
The jeweller will scratch the gold on a testing slab to take a sample of it and will then pour some acid (usually nitric acid) on the sample to see how it reacts.
Depending on the chemical reaction observed, the karat of the gold can be determined.
You can also purchase a testing kit with nitric acid and test the gold yourself. Here is how such a test is usually performed:
Scratch the gold on the testing stone provided so that the piece leaves a mark.
The kit will contain bottles with acid of varying concentration, and each will have a karat number written on its label. Drop a little acid from the bottle with the lowest karat number on the scratch mark and observe the reaction.
If the gold is a higher karat than the label on the bottle, then you won't see any change in the mark's color. In such a case, repeat second step by using the bottle labeled with the next lowest karat number.
If the gold is the same karat as the number on the label, or within +/- 1 karat of it, the color of the mark will change, but only slightly.
If the gold's karat is more than 1 karat lower than the number on the bottle, then the portion of the mark where acid has been applied will be dissolved and will disappear.
Don't forget to read the instructions enclosed with the testing kit because the exact procedure might differ from the general method described above.
There are other methods to test the purity of gold that have become popular. However, despite their popularity, they are actually close to useless.
Biting a gold piece is said to be a good indicator of whether it is real, as gold is a very soft metal. However, there are many other metals that are also soft and can be covered with gold plating to make them look like gold, so biting them won't show you conclusively whether you're dealing with gold.
It is also said if a gold piece is not attracted to a magnet, this is a proof that the item is actually made of gold. However, there are many other metals that are non-magnetic, which can also be plated with gold and will not react to a magnet.
The best way to determine the purity of a gold item is to test it with acid and also make sure that the piece is not made of another metal covered with a thin layer of gold.