How to recognize gold?

You've just inherited your great-aunt Yvette's entire jewelry collection, and among the costume jewelry and objects from another era, you've spotted a few pieces whose value you're wondering about? Is this large gold-colored necklace actually gold? And is this cuff bracelet platinum, perhaps palladium, or white gold? Let's look at a few little tips for testing the quality of your gold jewelry yourself, at home.

Contents:

• Look for the hallmark
• Testing gold with vinegar
• The magnet test
• Bleach to identify gold
• Ceramic
• The bite test
• The polishing cloth

Look for the hallmark

This should be your very first reflex. Gold jewelry, like silver jewelry and jewelry made from precious metals, is systematically hallmarked. A hallmark is a marking on the metal that proves its quality and authenticity. So, to answer the question "How do you identify gold?", the simplest and quickest answer is: find the hallmark.

Please note that in France, this marker is only mandatory on jewelry containing more than three grams of gold. If it contains less, it may not be hallmarked.

Thanks to it, you now have two indications:
the gold content of your jewelry
the authenticity of your piece
We then speak of "carats" (which is not, in this case, the unit used to measure diamonds), but rather a unit of measurement in jewelry that gives an idea of a metal's purity.

The carat is denoted by the letter "k".

Which hallmark for which gold carat?

There are two types of hallmarks used to authenticate your gold alloy jewelry: the maker's mark (the manufacturer) or the responsibility mark (the importer). The latter generally takes the shape of a diamond.

The other is known as the "fineness or guarantee mark". Applied by customs, it varies according to the gold content of your jewelry.

24-carat gold is represented by a seahorse, but it is too malleable to be used in jewelry.
18-carat gold is authenticated by an eagle's head.
14-carat gold (around 58.5% gold) is represented by a scallop shell.
9-carat gold, whose alloy contains at least 37.5% gold, is authenticated by a clover-shaped hallmark.

Testing gold with vinegar

Yet more proof that vinegar really is useful for everything, since you can even test the purity of your jewelry with it. To do so: place your gold-colored jewelry in a container filled with vinegar and leave it for at least an hour. Afterwards, rinse your pieces with water.
Do you notice a difference in color? If so, your jewelry is not gold. If the color has not changed, there is a good chance that it is genuine gold.

The magnet test

Today's little science minute: gold is not magnetic. So I'll let you work out for yourself what it might mean if your large gold-colored signet ring ends up firmly attached to a magnet. Yep, disappointment is yours.
None of your gold-colored necklaces, pendants, or other bracelets are gold if they are magnetic.

Bleach to identify gold

Simple and effective, although you will need to wait at least 24 hours before getting an answer; still, it's a tip like any other.
Place your jewelry in a bleach solution for a full day and observe the results. If there is oxidation, there will be disappointment. But if your jewelry has not oxidized, then it really is gold!

Ceramic

First of all, a warning is in order. The ceramic test for identifying gold jewelry should only be used as a last resort, as this technique can damage your precious piece. 
To carry it out, you will need unglazed ceramic, meaning without enamel. Rub your jewelry against it and analyze the result. If a golden mark appears on the ceramic, your jewelry is gold; if it leaves a black mark, it is not gold.

The bite test

If you bite a small corner of your bracelet or your favorite hoop earrings and your tooth leaves a mark, your items are gold. This phenomenon is due to gold's malleability. Incredible, isn't it?

The polishing cloth

Easy and quick, you will only need a small polishing cloth, generally used for cleaning jewelry, to carry out this test. 
Rub your ring, bracelet, or long necklace on it and observe the result. If the gold-colored layer has dulled or reveals another color, unfortunately your piece is not gold, but most likely gold-plated—that is, covered with a very thin layer of gold that can deteriorate.

You can entrust this task to a professional jeweler or a gold-buying store. Gold testing is free, so you will not have to pay for the procedure. This could help you avoid potential accidents with your jewelry. 

Finally, please note that gold and gold-plated jewelry, which is made from a brass alloy (copper and zinc) and coated by electrolysis with a thin 3-micron layer of gold, are two different things. There are also many varieties of gold used in jewelry: black gold, yellow gold, rose gold, white gold, and even rhodium-plated gold, for example.