You can test gold in several ways, ranging from simple checks you can do yourself at the kitchen table to chemical and professional methods that give a reliable answer. Start by looking for a hallmark, try a magnet and see whether the jewellery has discoloured your skin. If you want to know for certain - and how pure the gold is - you'll need an acid test or let a goldsmith measure it. No single home test alone proves that gold is genuine, but several tests together give a good indication.

Here the methods are reviewed one by one, so you know what each test can tell you, and what it cannot.

Find the hallmark first

The quickest place to start is the jewellery's hallmark. Genuine gold is almost always stamped with an indication of its purity, and it is typically located on the inside of a ring band, on the clasp of a necklace or on the back of a pendant. You are looking for numbers like 585 or 750, which indicate the number of thousandths of pure gold. 585 corresponds to 14 carat, 750 to 18 carat. You may also come across carat indications written as a number followed by K.

A hallmark is strong evidence, but not conclusive proof. Hallmarks can be imitated, and older or homemade jewellery sometimes lacks them, even though the gold is genuine. A missing hallmark therefore does not automatically mean the gold is fake - it just means you need to use another method to confirm it.

The magnet test reveals the obvious fakes

Gold is not magnetic. Hold a strong magnet - preferably a neodymium magnet - close to the jewellery. If the jewellery is drawn towards the magnet or snaps onto it, it contains magnetic metals like iron or nickel and is not pure gold.

The test has a clear limitation. The fact that a piece of jewellery is not attracted to the magnet does not prove it is gold, because several other non-magnetic metals, such as brass and copper, pass the test just as easily. The magnet therefore only weeds out the most obvious fakes and should be followed up by a more precise method.

Look for discolouration of skin and jewellery

Genuine gold does not tarnish and does not rust. If a piece of jewellery leaves green or black streaks on the skin, or has itself developed dark spots, it suggests that it is a base metal or a very thin gold plating over another metal. Gold does not react with sweat and air in that way.

Here it is worth knowing the difference between pure gold and gold-coloured alloys. Even genuine gold is mixed with other metals to make it hard enough for jewellery, but the proportion of gold in, for example, 14K gold is high enough that the jewellery does not discolour the skin under normal use. If the skin starts to turn dark, it is a sign that there is too little or no gold at all in the piece.

The acid test shows both authenticity and carat

The most widely used test that actually determines the carat content is an acid test. The principle is that nitric acid dissolves base metals, but not pure gold. You lightly scratch the jewellery against a testing stone, so a streak of metal is deposited, and then drop an acid of a known strength onto the streak. If the streak reacts - fizzes or disappears - the gold is of lower purity than the acid corresponds to. If the streak remains unchanged, the gold holds at least the carat the acid is intended for.

Acid tests are sold as kits with bottles for different carat grades, so you can narrow down the purity by trial and error. The method is far more reliable than magnet and hallmark together, but the acid is corrosive and must be handled with gloves, safety glasses and good ventilation. The test also leaves a small scratch on the jewellery. If the piece is valuable or has sentimental value, you should therefore consider a method that does not touch the surface.

Weight and density as an extra check

Gold is a heavy metal. Pure gold has a high density, and that property can be used for a home test if you have an accurate scale. The method is based on the fact that a piece of genuine gold weighs more than a piece of the same size in a lighter metal such as brass or gilded zinc.

The classic approach is to weigh the jewellery dry and then weigh it submerged in water. The difference tells you how much water the jewellery displaces, and from that the density can be calculated. The method requires patience and an accurate scale, and it becomes imprecise with jewellery containing stones, cavities or several different metals. As a supplement to the other tests, however, it can help catch fakes that otherwise look genuine.

When should you go to a goldsmith?

If you want a reliable answer without scratching or etching the jewellery, a goldsmith or a gold buyer is the right place. Professionals use, among other things, X-ray-based measurement, which reads the jewellery's precise composition without touching the surface, and they can determine both authenticity and carat within moments. This is especially relevant if the jewellery is expensive, old or has stones you do not want to risk damaging.

A goldsmith can also assess things a home test overlooks, for example whether a piece of jewellery is gold-plated rather than solid gold. A gilded piece can pass both the magnet and surface tests, because the outer layer is actually gold, while the core is another metal. Here a professional measurement is the only reliable way to tell the difference.

Does the same apply to white gold?

White gold is tested according to the same principles as gold, because it is still gold - just alloyed with white metals and often coated with rhodium to achieve the cool, silvery sheen. The hallmark is read in the same way, 585 means 14K white gold just as with gold, and the acid test works here too.

What you need to be aware of is the rhodium coating. It wears off over time, and a surface test can react differently depending on whether the coating is intact or worn. If you want to know more about what white gold actually is, and how it differs from gold, you can read about what white gold is and about whether white gold is more expensive than gold. Both metals recur in jewellery in both gold and white gold.

What does carat mean once you have tested the gold?

When a test shows that the gold is genuine, the carat number tells you how pure it is. Carat indicates the ratio between pure gold and the other metals in the alloy, and 24 carat is pure gold. 14 carat means that 14 out of 24 parts are gold, while the rest are other metals that make the gold strong enough for daily use. That is why 14K gold is a common choice for jewellery that needs to be worn every day.

Both the hallmark and the acid test point towards the carat number, but if you want to understand how to read and interpret the numbers, you can dive into how to tell the carat of gold and into the question of which carat of gold is best. For silver jewellery a similar logic applies, where the hallmark 925 indicates sterling silver - you can read more about that under what 925 means in a ring.

How to combine the methods

No single home test alone proves that a piece of jewellery is genuine gold. The strength lies in stacking the signs on top of each other. Find the hallmark, check with the magnet, look for discolouration, and if all three tests give the green light, the probability of genuine gold is high.

If there is still doubt, or you need a definitive answer on both authenticity and purity, an acid test at home or a professional measurement at a goldsmith is the next step. The more the jewellery means - financially or emotionally - the more reason there is to let a professional determine it with a method that leaves no mark on the gold.