A diamond's hallmark is invisible to the naked eye. It corresponds to a number, and so it cannot be separated from the stone that bears it. This allows for better traceability of diamonds, from the source all the way to the delivery of a piece of jewelry.
Thanks to the hallmark, it is easier to make sure the diamond comes from a mine that is responsible in human and environmental terms.
This criterion now matters to a growing number of consumers. They want to keep buying jewelry set with white diamonds, especially engagement rings.
But they also want a guarantee proving that these diamonds were produced with a certain respect for people and the environment.
For some companies, the diamond hallmark has even become a selling point, as a way to prove the geographic origin of their stones. This is notably the case in Canada.
It also helps prevent fraud and jewelry store burglaries, since hallmarked diamonds can be traced.
How can you tell if a diamond in a piece of jewelry is real?
If you own one or more pieces of jewelry and have doubts about the stones set in them, there are a few simple tests you can do to find out whether you are looking at a real white diamond or an imitation.
The fog test
Breathe on the stone so that it fogs up. If the fog disappears immediately, it is very likely a white diamond.
The light test
If there is one property we associate with diamonds, it is their brilliance. Because its main color is white and its refractive index is high, a diamond reflects light back when it is well lit. You can test this by holding your jewelry under a bright light.
Be careful, though: some other white stones have a brilliance that looks remarkably like a diamond's.
Moissanite is one example.
The loupe test
Another essential property of diamond is its hardness. It ranks 10 on the Mohs scale, which makes it the hardest stone in the world. As a result, diamond does not scratch. If you look at your jewelry under a loupe and notice scratches or scuffs, the stone is not a diamond.
The heat test
This may sound strange, but you can test the stone in your jewelry by touching it with your tongue to feel its temperature.
This test relies on another property of diamond: thermal effusivity, which is a material's ability to impose its temperature on whatever it touches. Diamond has a very high effusivity (60,000).
In a room at 20 degrees Celsius, it will be less "influenced" by contact with our skin at 37 degrees, and will therefore feel colder than some white imitation stones such as zircon.
The metal the stone is set in
A precious stone goes hand in hand with a precious metal. Look at the hallmark on the metal your stone is set in. If it is 18- or 24-karat gold (eagle's head hallmark) or silver (Minerva hallmark), there is a better chance that your stone is a diamond.
Keep in mind, however, that the best proof remains a certificate of authenticity issued by one of the three internationally recognized gemological laboratories: GIA, HRD or IGI.
An appraisal by your diamond dealer can also give you more information and help you interpret that certificate.
In this article, we also explain how to tell the difference between a natural diamond and a lab-grown diamond: read the article
How can you tell if a piece of jewelry is valuable?
A few clues can help you figure out whether your jewelry is valuable.
Hallmarks proving the presence of precious metals
As mentioned above, a high-quality stone will never be paired with just any metal, but with gold or silver. So start by checking the hallmark on the metal your diamond is set in. Gold from 18 to 22 karats is stamped with an eagle's head. Silver is stamped with the head of Minerva.
A consistent color
Precious metals such as gold and silver keep a stable color, whether you wear them every day or keep them in a jewelry box.
If your jewelry changes color over time, it is most likely worth less.
The magnet test
Gold and silver are diamagnetic, so they should not move when a magnet comes near them. If they do, your jewelry was probably made with other metals.
The weight of the piece
To be hallmarked, a piece of jewelry that complies with European regulations must weigh at least 5 grams. This applies per piece: a pair of earrings must therefore weigh at least 10 grams. Below that weight, your jewelry will not be hallmarked.
How big is a 1-carat diamond?
It is important to note that the carat is not a measure of size but of weight (0.2 grams).
In other words, for the same quality, a 0.5-carat diamond will not be half the size of a 1-carat diamond. Its price, however, will be half as much.
Just to give you an idea, a 1-carat diamond measures about 6 mm in diameter.
That said, the eye does not register a diamond's dimensions so much as its volume and its brilliance. A cut optimized for the stone's quality and size will best bring out the diamond's visual qualities.
More than the number of carats, what really matters is the quality of the diamond and the skill of the diamond cutter.
As you can see, the hallmark is a mark of both quality and traceability, for diamonds as well as for jewelry.
A growing number of customers pay close attention to it.
