How to find out what metal my piece of jewellery is made of ? How many carats ?

Even before going to a scrap gold dealer shop or sending your jewellery by post, it is a good thing to know what your jewellery are made of. Indeed, very few pieces of jewellery are made of pure gold. It will help you to root out scammy buyers that could tell you that your necklace is in silver and not in gold or that it is 14 carat gold instead of 18 carat.

In this article we are going to learn about the different ways to gather information about a specific piece of jewellery.

It is not possible to the naked eye to be able to differentiate 9 carat gold from 14 carat gold or 18 carat gold from 14 carat. Or sometimes it is not even gold but platinum...

This carat number represent the purity/proportion of precious metal within the piece of jewellery. 24 carats is pure gold. We sometimes directly use the proportion such as 750 for 18 carat or 999 for 24 carat gold. I think it is easier but it is very frequent to hear about 18 or 9 carat gold.

Except in some part of Asia, jewellery is almost never 24 carat. Gold in its pure form is too soft and would distort over time when worn regularly. Usually some other metal (silver, copper ...) is added to harden the item.

Investment coins and bullion very often are in pure gold (24K) but there are also many coins that are in 22 carat (91.6% gold) for the same reason.

To find out if jewellery is 18 carat gold or just worthless gold plated, there are several ways to find out :

We 'll first talk about the not so efficient ways to do it that you could find on the Internet.

Not so efficient methods

How about using a magnet ?

Generally not very effective but you will find it a lot on the Internet. Approaching a magnet near jewellery; if the item is attracted by the magnet, it is not gold, nor silver nor platinum. This method is true but inefficient because in the end it just tells you if the piece is in iron or steel.

This method cannot help you to find out if the item is made of silver, gold, copper or platinum. Recall that there are many cheap jewellery pieces that are in a copper alloy, it looks yellow but is worthless.

it is especially true with fake coins. It looks like a gold coin but is made of copper. Using a magnet will not be enough to differentiate between copper and gold. Same thin with any non ferrous metal such as aluminium, nickel, lead, tin...

What about using bleach ?

Another commonly heard of method is to apply a tiny bit of bleach on a silver jewellery or silver metal. According to this popular belief, a silver item will blacken, while a silver plated item will not blacken. This is of course completely false! .

You just need to understand that a silver plated item is: The core of the item is made of any metal but it is covered with a thin silver layer. As a result, if you apply bleach, whether the core of the piece is made of silver or if there is silver just on the surface, it will darken because the bleach will react with the metal on the surface of the item !

Methods that work: Looking at hallmarks

On each piece of jewellery there are tiny markings named Hallmarks. This is a vast topic that I have covered in this article : Gold and silver hallmarks

The good thing with hallmarks is that everybody has a pair of eyes and can use them to read these hallmarks !

Granted, you might need a magnifying glass as these hallmark markings are really small. Usually they are hidden in such a way that when the piece of jewellery is worn, they are not visible.

For example, on a ring, you can see them on the part that is in contact with the skin. For a necklace, they are usually not far from the clasp, near your neck. Same thing with bracelets, they are not far from the clasp.

If you can't find any hallmarks, I have got bad news for you, it is not gold or any other precious metals. Most likely it is gold or silver plated. Even platinum has its own set of hallmarks so really jewellery without hallmarks is usually worthless.

There are also hallmarks on silverware. Why don't you check out your own silverware to search for the hallmarks ?

All this is well and good but professionals do not trust hallmarks. Some dishonest goldsmiths or jewellers apply fake hallmarks. Most often, they would apply a 18 carat hallmark on some 9 or 14 carat gold item.

Touchstone and acid testing

Professionals usually prefer acid testing to get this information. They will scratch a tiny bit of the piece of jewellery on the touch stone.

Then they apply a different set of acid on the touchstone and the little metal that has been extracted from the scratching.

Depending on there is a reaction with the acid or not, the jeweller is able to tell if the item is in gold and whether it is 9 carat, 14 carat, 18 carat, 22 carat or 24 carat gold.

It works very well for jewellery and other small objects.

However it doesn't really work for items that are much bigger. I have heard of scrap gold buyer that got scammed with fake bullion. The bullion surface is gold indeed (about 1mm layer of gold). But deeper, it is not gold.

Because acid testing only tests the metals on the surface, it failed to assess if the bullion is really made of gold or not. The photo above shows tungsten rods within a fake gold bullion.

Still, acid testing is enough to detect gold plated items from real gold. In case of gold plated, the layer is so thin (1µm) that when scratching the item on the touchstone, that surface gets removed and it is the metal below that gets tested.

This kind of testing set is not reserved for professionals and you can buy a set of acids and a touchstone for £50-80 on Amazon :

Gold-, Silver- and Platinum testing set - Gold-Tester, testing acid, carat – Test gold, silver and platinum in a reliable and fast way

Densimetric analysis - gravity gold tester

Gold is very heavy and densimetric analysis uses this fact to estimate the gold purity of jewellery.

These machine are based on similar scales that are made to weight relative density of materials (densimeter) in other industries such as science and engineering. In lay men's terms it will measure and tell you how many Carat Gold and purity your item is.

These scales through hydrostatic weighing, measure the Relative density of a substance. These scales are commonly used in the jewellry industry to test precious metals such as Gold, Platinum, Silver and other alloyed precious metals for their purity.

In essence, regardless if have a piece of jewellery is marked 24K or a piece of gold you think is 99% this machine will tell you the exact amount of gold in that item. For jewellers this device is especially warranted because a scratch/acid test will fail if a piece of jewellry is coated/plated/rolled with a pure or high karat gold and have other alloys underneath. In this circumstance a scratch test will show an a piece of jewellery more valuable than it is. The densimeter will not be susceptible to this fault because it measures the pieces relative density to water; taking a dry, then an underwater weight, which works out it's true relative density, thus it's exact gold content in karat or percentage

Want to buy one ? No problem cost is around £2000. At these prices, we are entering the world of real professionals. But still, there are issues with this kind of machine. Recall the fake bullion above ? There are rods of tungsten within it. Why tungsten ? Because the density of tungsten is very similar to gold.

So to say it another way, this gravity gold tester is not enough to identify fake bullion from genuine ones.

Spectrometric analysis

Spectrometric analysis is a non invasive method used when acid testing is not enough.

Welcome to the Rolls Royce of precious metals testing. You won't be able to fool a professional equipped with this machine.

Spectometric analysis is the most reliable way to find out what metal an item is made of.

The way it works is that some UV rays are sent across the item to detect the presence or absence of a given metal. It doesn't matter if there are several layers of metal, you'll know about them.

I have seen it working, it is amazing : it is like a pistol that gives you in a matter of seconds the purity of jewellery.

After using it for some time I had a few surprises. Some very costly pieces of jewellery from a very famous and well known brand (more in clothing but still sells some jewellery) are just plain shit. The piece was supposed to be a 18 carat item (75% gold) as described by its hallmark but it had only 66% gold (so 16 carat) after spectrometric analysis.

Quality and efficiency has a price. Such machines are sold around £10,000. I am pretty sure that you understand why most scrap gold dealers only have acid testing kits that can be bought on Amazon for £50 !

We introduced in this article the reliable methods that some professionals use and the less reliable ones you can read about on the Internet. The most reliable method for individuals like you and me is acid testing that can be bought for £50 and gives decent results. But for complex cases, nothing is better than spectrometric analysis, available on sale at around £10,000.