The term “real gold” in its popular usage does not necessarily imply that a piece of jewelry is made of pure gold. It is usually the case that the gold used in jewelry is mixed with other metals to make the resulting alloy harder and less prone to bending.
Real gold jewelry is made of a solid gold alloy, whose gold content is above a certain threshold. In the United States, for example, pieces containing less than 58.3% gold (10 karats) are not considered gold for commercial purposes.
What people usually refer to as fake gold is jewelry that is made of another metal (such as nickel, copper, silver, etc.) and covered with a layer of gold (gold plated) or with a thin gold sheet (gold filled).
How to Tell If Gold Is Real
Below are some of the more reliable ways to test jewelry for gold:
Testing gold with nitric acid is a pretty reliable way to tell how pure a gold alloy is.
The piece being tested is scratched against a testing slab so as to leave a scratch mark on it.
Then, nitric acid of varying concentrations is applied to the mark to see whether it will be dissolved.
Depending on the concentration of the acid that causes the mark to be dissolved, the purity of the alloy can be inferred.
This test can be performed at the jewelry store by a jeweler or at home, by using a gold testing kit and following the instructions that come with it.
You should keep in mind that the scratch should be deep enough so that you can get to the material beyond the top layer of the jewelry.
Otherwise, if the piece is gold plated or gold filled, a light scratch might only rub off the top gold layer, and the test will show that what you have is indeed gold.
Karat markings on jewelry indicate its purity. For example, a “10K” mark means that the jewelry is 10 karats, meaning that in every 24 parts alloy there are 10 parts gold.
European jewelry is often marked with parts-per-thousand markings instead of karat hallmarks. For example, if you see a mark that reads “417”, this corresponds to 10 karats, which in turn corresponds to 41.7% purity (10 divided by 24).
It is important to look for any markings next to the karat or purity number that might indicate that the jewelry is gold plated or gold filled.